Carbonate Petrography

Carbonate petrography is the study of limestones, dolomites and associated deposits under optical or electron microscopes greatly enhances field studies or core observations and can provide a frame of reference for geochemical studies.

25 strangest Geologic Formations on Earth

The strangest formations on Earth.

What causes Earthquake?

Of these various reasons, faulting related to plate movements is by far the most significant. In other words, most earthquakes are due to slip on faults.

The Geologic Column

As stated earlier, no one locality on Earth provides a complete record of our planet’s history, because stratigraphic columns can contain unconformities. But by correlating rocks from locality to locality at millions of places around the world, geologists have pieced together a composite stratigraphic column, called the geologic column, that represents the entirety of Earth history.

Folds and Foliations

Geometry of Folds Imagine a carpet lying flat on the floor. Push on one end of the carpet, and it will wrinkle or contort into a series of wavelike curves. Stresses developed during mountain building can similarly warp or bend bedding and foliation (or other planar features) in rock. The result a curve in the shape of a rock layer is called a fold.

Amethyst Gemstone

What is Amethyst?

Amethyst is a violet variety of quartz often used in jewellery. The name comes from the ancient Greek ἀ a- ("not") and μέθυστοςméthystos ("intoxicated"), a reference to the belief that the stone protected its owner from drunkenness. The ancient Greeks wore amethyst and made drinking vessels decorated with it in the belief that it would prevent intoxication. It is one of several forms of quartz. Amethyst is a semiprecious stone and is the traditional birthstone for February.

Amethyst colour

The colour in amethyst from most localities is unevenly distributed in the individual crystals. In amethyst geodes it is often most intense in the growth zones under the rhombohedral faces (at the tips). Occasionally the colour is deeper under either the r or z rhombohedral faces, giving the crystal a pinwheel appearance when viewed from the top. In prismatic crystals the colour may appear in phantom-like thin layers, while in sceptres and skeleton quartz the colour is often concentrated along the edges, and accompanied by smoky zones. Despite the intense colour, the content of iron occupying Si positions in amethyst is rather low, in the 10-100 ppm range.

When heated to more than about 300-400°C, amethyst loses its violet colour and often turns yellow, orange or brown, and then resembles the quartz variety citrine, but depending on the locality and the temperature during the heat treatment it may also turn colourless or rarely green.
Irradiation with UV light will also destroy the colour centres, and accordingly prolonged exposure to sunlight will slowly fade amethyst. The photo to the right shows the effects of heat (bottom left and right) and UV irradiation (top right) on the colour of a specimen from Uruguay.
Amethyst is pleochroic when the polarisation of the light is changed from parallel to the c-axis to perpendicular to the c-axis, amethyst changes its colour from blue-violet to purple. The strength of the effect varies to a considerable degree, and changes in the hue depending on the direction of the transmitted light may be observable with the naked eye, in particular in crystals with a zonar development of colour, which may even show sky-blue tones.

Amethyst Crystals


Amethyst crystals do not get very large, crystals longer than 30 cm are very rare. It is found in various forms and shapes, the most common growth forms are: 
  1. Druzy crystal aggregates that outline cavities; the crystals are usually short-prismatic and often lack prism faces. Most common in volcanic rocks, but also in hydrothermal veins, and even in cavities in sedimentary rocks;
  2. Scepters (late syntaxial overgrowth) on other color varieties of quartz, in particular in high- to medium-temperature environments like alpine-type fissures and pegmatites
  3. Split-growth crystals ("artichoke quartz") in hydrothermal veins in ore deposits, but also in volcanic rocks.
  4. As individual well-formed crystals in small cavities and fissures, in particular in volcanic rocks. 
  5. As hydrothermal vein filling, often with several growth phases with variable color that cause a banding pattern.

Occurrences

Amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks. Many of the hollow agates of southwestern Brazil and Uruguay contain a crop of amethyst crystals in the interior. Artigas, Uruguay and neighbouring Brazilian state Rio Grande do Sul are large world producers exceeding in quantity Minas Gerais, as well as Mato Grosso, Espirito Santo, Bahia, and Ceará states, all amethyst producers of importance in Brazil.
It is also found and mined in South Korea. The largest opencast amethyst vein in the world is in Maissau, Lower Austria. Much fine amethyst comes from Russia, especially from near Mursinka in the Ekaterinburg district, where it occurs in drusy cavities in granitic rocks. Many localities in south India yield amethyst. One of the largest global amethyst producers is Zambia in southern Africa with an annual production of about 1000 tonnes.
Amethyst occurs at many localities in the United States. Among these may be mentioned: the Mazatzal Mountain region in Gila and Maricopa Counties, Arizona; Red Feather Lakes, near Ft Collins, Colorado; Amethyst Mountain, Texas; Yellowstone National Park; Delaware County, Pennsylvania; Haywood County, North Carolina; Deer Hill and Stow, Maine and in the Lake Superior region of Minnesota, Wisconsin and Michigan. Amethyst is relatively common in the Canadian provinces of Ontario and Nova Scotia. The largest amethyst mine in North America is located in Thunder Bay, Ontario.

Amethyst types

Purple Amethyst

Purple Amethyst has been highly esteemed throughout the ages for its stunning beauty and legendary powers to stimulate, and soothe, the mind and emotions. It is a semi-precious stone in today’s classifications, but to the ancients it was a “Gem of Fire,” a Precious Stone worth, at times in history, as much as a Diamond. It has always been associated with February, the month the Romans dedicated to Neptune, their water-god, and is the traditional birthstone of that month. It is the stone of St. Valentine and faithful love, and signifies ecclesiastical dignity as the Bishop’s Stone. It carries the energy of fire and passion, creativity and spirituality, yet bears the logic of temperance and sobriety.

Brandberg Amethyst

Brandberg Amethyst is a unique and extraordinary blend of Amethyst, Clear and Smoky Quartz together in one exceedingly high-vibrational crystal. It is found only in Namibia, Africa, and is imbued with remarkable phantoms, enhydros, and other rare formations and inclusions. It attunes to pure consciousness and is a potent talisman of healing and perfection with the capacity to restore one back to their etheric blueprint in order to realign with the Divine Source.

Chevron Amethyst

Chevron Amethyst displays v-shaped chevrons of deep purple and white Quartz that “seep” into beautiful layers. It is one of the finest Third-Eye stones for stimulating vision within the self as well as the physical world, filtering the life force from the cosmos via the Crown in its white layers and opening up spiritual and psychic channels through the purple. It has a strong, focused energy for dissipating and repelling negativity, and is the perfect crystal for learning any form of spiritual healing. Hold one in each hand for powerful but safe out-of-body travel, shamanic journeying or pathworking, and between the hands while praying or reciting mantras.

Cacoxenite in Amethyst 

Cacoxenite in Amethyst mingles dark brown to yellow tufts of Cacoxenite, a phosphate mineral and major component in the Super Seven crystal, with the host crystal Amethyst. This combination brings a high level of creativity and new ideas to humanity by fostering thoughts that have never been thought of before. It is a calming stone, good in times of upheaval, and raises spiritual awareness of the creator essence in the beauty of nature and the kindness in people. Carry on the night of the crescent and full moon to transfer healing energy to the Earth and create an ethereal connection between all of the universe.

Rutiliated Amethyst

“Rutilated” Amethyst is a rare form of Amethyst which appears to contain Rutile, but actually contains brownish crystals of Goethite, an iron hydroxide mineral also found in the Super Seven crystal. Goethite is a stone for finding the link between the deep self and Earth, and together with Amethyst clears the Earth and Base Chakras, aligning the whole chakra system to the higher mind. It purifies the emotional body and is particularly helpful in grief work. It facilitates clairaudience, communion with angels, and connections with other worlds. To program as a wishing stone or with intentions, messages, and prayers, simply hold the stone with the intent in mind.

Amethyst Healing Properties

Amethyst is a wonderful talisman for use in the creative arts, especially in darker shades. It assists endeavours where new, original results need to be created using tools and methods of the past. It is often used as the Artist’s Stone, the Composer’s Stone, the Inventor’s, Poet’s and Painter’s Stones. Keep an Amethyst crystal or cluster in the area to focus and amplify the creative elements of the Universal Life Force.
Called the “All-healer,” Amethyst is one of the most effective crystals for healing people, plants and animals. Natural unpolished Amethysts or geodes are particularly helpful placed where plants will not grow or animals refuse to sit. It also counteracts negative earth energies beneath buildings or anywhere that feels hostile. 
Amethyst protects against psychic attack, paranormal harm or ill-wishing, and returns the energy back to the universe after being transformed into positive, loving energy. To increase this power and attract good luck, draw an image of the sun and the crescent moon over an Amethyst in lavender incense smoke. 
Referred to as “nature’s tranquilliser,” Amethyst calms and soothes, assisting the transmission of neural signals through the brain. It relieves obsessive compulsive disorder and hyperactivity in children and animals. Place under the pillow or mattress, or rub the centre of the forehead counter-clockwise to cure insomnia and stimulate pleasant dreams. It is especially effective for children’s recurring nightmares and fears of the dark, and may help alleviate homesickness.
Amethyst is an excellent stone for diplomats, negotiators and business people. It calms angry temperaments and gives a distinct advantage in situations where debating is required. Wear or hold Amethyst to bring in spiritual insights coupled with intellectual reasoning. As a luck and prosperity crystal, Amethyst is good for reducing the tendency to overspend, gambling addictions or unwise investments. 
Amethyst is connected to the Temperance card in the tarot, representing balance. It is a stone dedicated to curbing overindulgence and bad habits, and is an excellent aid to quitting smoking, drinking and drug use, as well as unhealthy physical passion. It also provides the strength needed to obtain freedom from addictive personalities, one’s own or another’s. Placing an Amethyst on the navel is believed to protect a person from intoxication, and in conjunction with other treatments such as counselling, helps cure addictions. A naval piercing makes it possible to always keep an Amethyst in this spot. 
Amethyst is the stone of St. Valentine and of faithful lovers because St. Valentine was thought to have worn an Amethyst ring engraved with the image of Cupid. It is also referred to as the “couple’s stone” and gives meaning to relationships that over time, transcends the carnal union and gives way to deeper connection and a more soulful communion. Wear as an engagement or eternity ring for fidelity, or as a locket to call back lost love.

Physical properties of Amethyst

Chemical FormulaSiO2
ColourPurple
Hardness7
Crystal SystemHexagonal
Refractive Index1.54 - 1.55
SG2.63 - 2.65
TransparencyTransparent to translucent
Double Refraction.009
LusterVitreous
CleavageIndiscernible
Mineral ClassQuartz

Amber Gemstone

What is Amber?

Amber is fossilised tree resin (not sap), which has been appreciated for its colour and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects. Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewellery.

Composition 

Amber is heterogeneous in composition, but consists of several resinous bodies more or less soluble in alcohol, ether and chloroform, associated with an insoluble bituminous substance. Amber is a macro-molecule by free radical polymerisation of several precursors in the labdane family, e.g. communic acid, cummunol, and biformene. These labdanes are diterpenes (C20H32) and trienes, equipping the organic skeleton with three alkene groups for polymerisation. As amber matures over the years, more polymerisation takes place as well as isomerization reactions, cross-linking and cyclization.

Formation

Molecular polymerisation, resulting from high pressures and temperatures produced by overlying sediment, transforms the resin first into copal. Sustained heat and pressure drives off terpenes and results in the formation of amber.
For this to happen, the resin must be resistant to decay. Many trees produce resin, but in the majority of cases this deposit is broken down by physical and biological processes. Exposure to sunlight, rain, microorganisms (such as bacteria and fungi), and extreme temperatures tends to disintegrate resin. For resin to survive long enough to become amber, it must be resistant to such forces or be produced under conditions that exclude them.

Distribution and mining

Amber is globally distributed, mainly in rocks of Cretaceous age or younger. Historically, the Samland coast west of Königsberg in Prussia was the world's leading source of amber. First mentions of amber deposits here date back to the 12th century. About 90% of the world's extractable amber is still located in that area, which became the Kaliningrad Oblast of Russia in 1946.
Pieces of amber torn from the seafloor are cast up by the waves, and collected by hand, dredging, or diving. Elsewhere, amber is mined, both in open works and underground galleries. Then nodules of blue earth have to be removed and an opaque crust must be cleaned off, which can be done in revolving barrels containing sand and water. Erosion removes this crust from sea-worn amber.
Caribbean amber, especially Dominican blue amber, is mined through bell pitting, which is dangerous due to the risk of tunnel collapse.

Geological record

Transparent Amber.
The oldest amber recovered dates to the Upper Carboniferous period (320 million years ago). Its chemical composition makes it difficult to match the amber to its producers – it is most similar to the resins produced by flowering plants; however, there are no flowering plant fossils until the Cretaceous, and they were not common until the Upper Cretaceous. Amber becomes abundant long after the Carboniferous, in the Early Cretaceous, 150 million years ago, when it is found in association with insects. The oldest amber with arthropod inclusions comes from the Levant, from Lebanon and Jordan. This amber, roughly 125–135 million years old, is considered of high scientific value, providing evidence of some of the oldest sampled ecosystems.
In Lebanon more than 450 outcrops of Lower Cretaceous amber were discovered by Dany Azar a Lebanese paleontologist and entomologist. Among these outcrops 20 have yielded biological inclusions comprising the oldest representatives of several recent families of terrestrial arthropods. Even older, Jurassic amber has been found recently in Lebanon as well. Many remarkable insects and spiders were recently discovered in the amber of Jordan including the oldest zorapterans, clerid beetles, umenocoleid roaches, and achiliid planthoppers.
Baltic amber or succinite (historically documented as Prussian amber) is found as irregular nodules in marine glauconitic sand, known as blue earth, occurring in the Lower Oligocene strata of Sambia in Prussia (in historical sources also referred to as Glaesaria). After 1945 this territory around Königsberg was turned into Kaliningrad Oblast, Russia, where amber is now systematically mined.
It appears, however, to have been partly derived from older Eocene deposits and it occurs also as a derivative phase in later formations, such as glacial drift. Relics of an abundant flora occur as inclusions trapped within the amber while the resin was yet fresh, suggesting relations with the flora of Eastern Asia and the southern part of North America. Heinrich Göppert named the common amber-yielding pine of the Baltic forests Pinites succiniter, but as the wood does not seem to differ from that of the existing genus it has been also called Pinus succinifera. It is improbable, however, that the production of amber was limited to a single species; and indeed a large number of conifers belonging to different genera are represented in the amber-flora.
Semitransparent Amber.
Non-transparent (bone and foamy)

Amber Healing Properties

They may aid the emotions, and through their role to assist emotional healing they help to create a more positive outlook on life.
Their role within the sacral chakra means that it this a strong stone to help you to enhance your creativity.
These stones link the everyday self to the spiritual self.
It is known to be one of the better natural crystals to use for protection from psychic attack.
This golden yellow resin is highly protective against any type of negativity, especially from psychic sources.
Amber stone has many wonderful qualities for healing the physical and emotional body. It is worth using as it may also heal health problems you forgot you had until they are gone.

Physical Properties of Amber

Chemical FormulaAmber is composed of complex organic material without any definitive chemical formula. Its inherent substance can also vary depending on its origination.
ColourBlue, Red, Green, Yellow, Orange, Brown
Hardness2 - 2.5
Crystal SystemAmorphous
Refractive Index1.539 - 1.545
SG1.0 - 1.1
TransparencyTransparent to nearly opaque
LusterResinous
CleavageNone

Origin of Earthquakes in the Hawaiian Islands

Where do earthquake travel-time curves come from?

Tsunamis Generated by Megathrust Earthquakes

How is Mars Compare to Earth?

Convergent Margin, Subduction to Tsunami

Divergent Boundary, Fast Spreading Ridge

Amazonite

What is Amazonite?


Amazonite (sometimes called "Amazon stone") is a green variety of microcline feldspar. The name is taken from that of the Amazon River, from which certain green stones were formerly obtained, but it is doubtful whether green feldspar occurs in the Amazon area.
A green to blue-green variety of K-feldspar, usually microcline, but sometimes applied to orthoclase. The colour is usually caused by an elevated content of Pb (up to 1.2% PbO).
However, there are also indications that the green colour of some microcline is caused by divalent Fe. Overenthusiastic uses of this name include giving this name to slightly gray-green hues in microcline that are often photosensitive and turn from greenish gray to light smoky gray. Sunlight can sometimes enrich the colour of genuine amazonite.

Amazonite properties

Mohs Hardness of 6-6.5 with a triclinic crystal structure. Amazonite or Microcline is a form of alkali feldspar, and it’s colour is due to the presence of lead. Although the main colour of Amazonite is teal it may also be partially colourless, white, yellow, pink, red, gray or green. It’s striking colour is due to the presence of lead and is that mineral that determines the depth of the colour.

Occurrence

Amazonite is a mineral of limited occurrence. Formerly it was obtained almost exclusively from the area of Miass in the Ilmensky Mountains, 50 miles southwest of Chelyabinsk, Russia, where it occurs in granitic rocks. More recently, high-quality crystals have been obtained from Pike's Peak, Colorado, where it is found associated with smoky quartz, orthoclase, and albite in a coarse granite or pegmatite. Crystals of amazonite can also be found in Crystal Park, El Paso County, Colorado. Other locations in the United States which yield amazonite include the Morefield Mine in Amelia, Virginia. It is also found in pegmatite in Madagascar and in Brazil.
Because of its bright green colour when polished, amazonite is sometimes cut and used as a cheap gemstone, although it is easily fractured, and loses its gloss due to its softness.
For many years, the source of amazonite's colour was a mystery. Naturally, many people assumed the colour was due to copper because copper compounds often have blue and green colours. More recent studies suggest that the blue-green colour results from small quantities of lead and water in the feldspar.

Amazonite healing properties

Amazonite assists in communicating one’s true thoughts and feelings without over-emotionalism. It also enables one to see a problem from another’s point of view in order to affect peace, or to see both sides of an issue objectively to resolve one’s own inner conflicts. Sleeping with an Amazonite can bring these components into focus through the symbolism of dreams. 
As a support stone, Amazonite aids in overcoming loneliness, and has been credited with making married life happier.
Amazonite is a Barrier Filter crystal that blocks geopathic stress, absorbs microwaves and cell phone emanations, and protects against electromagnetic pollution. Place it near computers and other electronics, or tape to your cell phone.
In the workplace, Amazonite dispels negative energy and aggravation, and protects against unfair business practices and others taking advantage. A stone of prosperity, Amazonite attracts new customers and orders to a business, and assists one in being in the right place at the right time for new opportunities.
Amazonite is a good luck stone for games of chance, competitions and luck in any financial venture. To make a lucky-charm, combine three Amazonites and a small amount of basil and mint in a small pouch. Leave it in front of a turquoise candle until the candle burns down.
Hide an Amazonite in a child’s or teen’s bedroom to encourage tidiness, and keep a dish of Amazonites on the kitchen table to persuade others to assist more with chores.

Physical Properties of Amazonite

Chemical FormulaKAlSi3O8
ColourBlue, Green, Purple, Gray, Multicolored
Hardness6 - 6.5
Crystal SystemTriclinic
Refractive Index1.52 - 1.53
SG2.56 - 2.58
TransparencyTranslucent to opaque
Double Refraction-.008
LusterVitreous
Cleavage2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal
Mineral ClassMicrocline

Agate Gemstone

What is Agate?

Agate is the name given to numerous varieties of banded Chalcedony, a mineral of the Quartz family. Its name comes from the Achetes River in Sicily, where Agates were first found. Usually banded in layers, or stripes, some varieties have "eye" markings, or specks of colour, some have fossilised inclusions, and others are solid. Called the earth rainbow, the concentric bands of Agate form in nearly every colour the earth can produce, including a colourless form.
It is a translucent variety of microcrystalline quartz. It is used as a semiprecious stone when it is of desirable quality and colour. Agate generally forms by the deposition of silica from groundwater in the cavities of igneous rocks. The agate deposits in concentric layers around the walls of the cavity, or in horizontal layers building up from the bottom of the cavity. These structures produce the banded patterns that are characteristic of many agates.
Coyamito Agate.

History

Historically, Agate has been discovered with the artefacts of Neolithic people, and was used as healing amulets and ornamentation dating back to Babylon. Its medicinal uses continued through the ancient Greek and Egyptian civilisations, and spread throughout Africa and the Middle East into Russia. Agate sparked a world renowned stone-cutting and polishing industry in Germany that flourished from the 15th to the 19th century, and exists today.
Petrified wood agate.
Metaphysically, Agate has a lower intensity and vibrates to a slower frequency than other stones, but is highly regarded as a stabilising and strengthening influence. The layered bands of microscopic quartz in Agate may appear delicate, they are actually very strong. Agate is excellent for balancing emotional, physical and intellectual energy, and in harmonising yin and yang, the positive and negative forces of the universe.

Agate occurs in a wide range of colours, which include brown, white, red, Gray, pink, black, and yellow. The colours are caused by impurities and occur as alternating bands within the agate. The different colours were produced as groundwater of different compositions seeped into the cavity. The banding within a cavity is a record of water chemistry change. This banding gives many agates the interesting colours and patterns that make it a popular gemstone.
Agua Nueva agate.

Types of Agates

The world of agates is a fascinating and ever evolving places. There are hundreds, if not thousands of types of agates. They are found around the world. They bring a wonder and magic to the planet with their swirls of colour bands.
Blue Lace Agate, Crazy Lace Agate, Dendritic Agate, Fire Agate, Laguna Agate and Moss Agate.
A matched pair of bookends cut from a large agate nodule.

Agate Gemstone

Agates have been used as gemstones for thousands of years. They were some of the earliest stones fashioned by people. Today they are cut into cabochons, beads, small sculptures, and functional objects such as paperweights and bookends. Agate cabochons are popular and used in rings, earrings, pendants, and other jewellery objects. Agate beads are commonly made into necklaces and earrings. Some have been used as marbles.

Tumbled Agate

Agate is the most popular rough for producing tumbled stones. It is generally inexpensive and can be tumbled with good results by beginners. It has a hardness of seven and can be loaded into a rock tumbler with jasper and any of the quartz varieties.

More About Agate

Most agate has unimpressive colours and patterns. However, agate is a porous material that readily accepts dye. Most of the spectacularly coloured agates sold in the gemstone trade have been dyed. Rarely, the colour patterns of an agate form interesting landscape scenes. These are sought after by collectors.

Moss agate

Moss agate contains green filament-like inclusions, giving it the superficial appearance of moss or blue cheese. There is also tree agate which is similar to moss agate except it is solid white with green filaments whereas moss agate usually has a transparent background, so the "moss" appears in 3D. It is not a true form of agate, as it lacks agate's defining feature of concentric banding.

Agate Healing properties

Metaphysically, Agate has a lower intensity and vibrates to a slower frequency than other stones, but is highly regarded as a stabilizing and strengthening influence. The layered bands of microscopic quartz in Agate may appear delicate, they are actually very strong. Agate is excellent for balancing emotional, physical and intellectual energy, and in harmonizing yin and yang, the positive and negative forces of the universe.

Blue lace agate

Blue Lace Agate has a soft, soothing elegance; like sky-blue waters released from winter's grasp. Its graceful, circular design has a stimulating, positive effect on emotions and attitude. It is not a stone of protection, but rather of encouragement and support. Its circular flowing energy calms, uplifts and elevates.

Crazy lase agate

Crazy Lace Agate is called the Laughter Stone, or "Happy Lace." It is associated with sunny Mexican fiestas and dancing, and brings joy to those who wear it. It is not a stone of protection, but of support and encouragement, elevating thoughts and promoting optimism. Its graceful design, in random lacy patterns, creates a circular flow of energy, stimulating for the mind and attitude.

Dendritic agate

Dendritic Agate is known as the Stone of Plentitude. It brings abundance and fullness to all areas of life, from business to agricultural endeavors. It was associated with the ancient Greek dryads, woodland and tree spirits, and was buried in the fields at the time of sowing to insure a good harvest.

Fire agate

Fire Agate, known as the spiritual flame of absolute perfection, carries a great mystery locked inside its deep brown crystal. You need only touch the stone and fiery embers ignite. Peer into its depths and flames leap within its chambers. Study it closely and it will almost show you its secrets.

Laguna agate

Laguna Agate is the most highly praised banded agate in the world. It is known for its extremely tight banding and vibrant shades of red and scarlet. Laguna Agate is found in an area covering roughly four square miles in a remote mountain range in the state of Chihuahua, Mexico.

Moss agate

Throughout history and all cultures, Moss Agate has been known as the crystal of gardeners and agriculture. It was considered a miraculous healing stone for tribal priests of the past, giving them power to interact with our human organic system, and was used as a talisman to make warriors strong and victorious.

Physical Properties of Agate

Chemical FormulaSiO2
ColourWhite, Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black, Banded, Multicolored
Hardness7
Crystal SystemHexagonal
Refractive Index1.54 - 1.55
SG2.63 - 2.65
TransparencyTranslucent
Double Refraction.009
LusterVitreous
CleavageIndiscernible
Mineral ClassQuartz (Chalcedony). 

Alexandrite gemstone

Alexandrite

Alexandrite is named after the Russian tsar Alexander II (1818-1881), the very first crystals having been discovered in April 1834 in the emerald mines near the Tokovaya River in the Urals. The discovery was made on the day the future tsar came of age. Although alexandrite is a relatively young gemstone, it certainly has a noble history. Since it shows both red and green, the principal colours of old Imperial Russia, it inevitably became the national stone of tsarist Russia.Beautiful alexandrite in top quality, however, is very rare indeed and hardly ever used in modern jewellery. In antique Russian jewellery you may come across it with a little luck, since Russian master jewellers loved this stone. Tiffany’s master gemologist George Frederick Kunz (1856-1932) was also fascinated by alexandrite, and the jeweller’s firm produced some beautiful series of rings and platinum ensembles at the end of the 19th and beginning of the 20th century. Smaller alexandrites were occasionally also used in Victorian jewellery from England.

Forming of Alexandrite

Alexandrite is the rare colour-change variety of the mineral chrysoberyl. Its rarity is a result of its unlikely chemical makeup. Alexandrite can only form when aluminium and beryllium combine with trace elements like iron, titanium and, most importantly, chromium. On rare occasion, vanadium may also be present. The unlikelihood of the rare element chromium being in the right place to combine with aluminium and beryllium under exactly the right conditions to create alexandrite is what makes it so rare and valuable


The magic of changing colours.

The most sensational feature about this stone, however, is its surprising ability to change its colour. Green or bluish-green in daylight, alexandrite turns a soft shade of red, purplish-red or raspberry red in incandescent light. This unique optical characteristic makes it one of the most valuable gemstones of all, especially in fine qualities.
Alexandrite is very scarce: this is due to its chemical composition. It is basically a chrysoberyl, a mineral consisting of colourless or yellow transparent chrysoberyl, chrysoberyl cat’s eye and colour-changing alexandrite (also in cat’s eye varieties). It differs from other chrysoberyls in that it not only contains iron and titanium, but also chromium as a major impurity. And it is this very element which accounts for the spectacular colour change. Rarely, vanadium may also play a part. According to CIBJO nomenclature, only chrysoberyls displaying a distinct change of colour may be termed alexandrite.
Like many other gemstones, alexandrite emerged millions of years ago in a metamorphic environment. But unlike many others, its formation required specific geological conditions. The chemical elements beryllium (a major constituent in chrysoberyl) and chromium (the colouring agent in alexandrite) have contrasting chemical characteristics and do not as a rule occur together, usually being found in contrasting rock types. Not only has Nature brought these contrasting rock types into contact with each other, but a lack of the chemical element silica (the second most common element in the Earth's crust) is also required to prevent the growth of emerald. This geological scenario has occurred only rarely in the Earth's history and, as a result, alexandrite crystals are very scarce indeed.

Alexandrite mining

Russia has remained the primary source of alexandrite since gems from the mines of the Urals became available on the market. When the Russian deposits were thought to have been exhausted, interest in the unique colour miracle decreased - especially since alexandrites from other mines hardly ever displayed the coveted colour change. But the situation changed dramatically in 1987, when alexandrites were discovered in a place called Hematita in Minas Gerais, Brazil. The Brazilian alexandrites showed both a distinctive colour change and good clarity and colour. Thus the somewhat dulled image of the miraculous stone received another boost. The colour of the Brazilian stones is admittedly not as strong a green as that of Russian alexandrite, but the colour change is clearly discernible. Today Hematita is one of the most important deposits of alexandrite in economic terms. Occasionally alexandrite with chatoyancy is discovered there, an effect which has not yet been observed in Russian alexandrite. Alexandrites are also obtained from sources in Sri Lanka, but the hue of these stones compares less than favourably with that of the Uralian alexandrites. They appear green in daylight and a brownish red in artificial light. The Tunduru area in southern Tanzania has also produced some outstanding specimens since the mid-1990s. Alexandrites are also found in India, Burma, Madagascar and Zimbabwe. Although this stone is still considered a rarity, specialised gemstone dealers do stock it, especially since improved trade relationships between Russia and the rest of the world have ensured a better supply of Russian alexandrites to the market.

Physical properties of Alexandrite

Chemical FormulaBeAl2O4
ColourBlue, Red, Green, Yellow, Pink, Purple, Gray, Multicolored
Hardness8.5
Crystal SystemOrthorhombic
Refractive Index1.744 - 1.755
SG3.5 - 3.8
TransparencyTransparent to nearly opaque
Double Refraction.009
LusterVitreous
Cleavage1,1 ; 3,2. Often exhibits parting along twinned crystals.
Mineral ClassChrysoberyl

Almandine

Almandine Gemstone

Almandine, also known incorrectly as almandite, is a species of mineral belonging to the garnet group. The name is a corruption of alabandicus, which is the name applied by Pliny the Elder to a stone found or worked at Alabanda, a town in Caria in Asia Minor. Almandine is an iron alumina garnet, of deep red colour, inclining to purple. It is frequently cut with a convex face, or in cabochon, and is then known as carbuncle. Viewed through the spectroscope in a strong light, it generally shows three characteristic absorption bands.


It is also a popular gemstone and the most widely used Garnet in the gem trade. More gemstones are faceted from Almandine than any other type of Garnet. Only a small amount of Almandine crystals are transparent and light enough for gemstone use; most of the Almandine found is rough and opaque and not gem quality. Some Almandine Garnets display asterism when polished as cabochons, and are known as "Star Garnets".

Occurence

Almandine is often embedded in a mica schists, and forms very nice matrix pieces with perfectly formed symmetrical crystals. The schist matrix often breaks up due to weathering, resulting in the Almandine crystals breaking loose into individual, perfectly formed floater crystals which may be quite large.

Almandine deposits

Almandine occurs rather abundantly in the gem-gravels of Sri Lanka, whence it has sometimes been called Ceylon-ruby. When the color inclines to a violet tint, the stone is often called Syriam garnet, a name said to be taken from Syriam, an ancient town of Pegu (now part of Myanmar). Large deposits of fine almandine-garnets were found, some years ago, in the Northern Territory of Australia, and were at first taken for rubies and thus they were known in trade for some time afterwards as Australian rubies.
Almandine is widely distributed. Fine rhombic dodecahedra occur in the schistose rocks of the Zillertal, in Tyrol, and are sometimes cut and polished. An almandine in which the ferrous oxide is replaced partly by magnesia is found at Luisenfeld in German East Africa. In the United States there are many localities which yield almandine. Fine crystals of almandine embedded in mica-schist occur near Wrangell in Alaska. The coarse varieties of almandine are often crushed for use as an abrasive agent.

Types of Almandine

Types of Almandine Garnet include Carbuncle, Merelini Mint Garnet, Thai Garnet, Grandite, and Precious Garnet. Some rare Almandine crystals from India or Idaho have asbestos inclusions that create a highly prized, star-like effect when faceted. Precious, or Noble Garnet, is deep red and transparent. Brown and opaque Almandine is ferrous and aluminum-like with traces of manganese and/or magnesium.

Healing properties of Almandine

In this article, the metaphysical properties of Almandine Garnet are explored. Almandine is a strong regenerative healing crystal bringing strength and stamina, and aids circulation and all blood related issues.
It is an excellent crystal for fertility, sexual potency and libido. Emotionally, Almandine cultivates a sense of security, safety and abundance. It is associated with the First Chakra and has the healing energy to help arouse the kundalini and keep those energies grounded.
It is a stone of physical love and relationships, and a spiritual stone of psychic protection. It increases willpower and resistance to all things negative. Almandine Garnet ranges in colour from light to deep scarlet, dark red, and muted shades of brown.
A host of angels are associated with its colour energies and it honours three Goddesses. Garnet is the traditional birthstone of January, and Almandine is the natural birthstones of those born in the first month of autumn and mid-autumn.
Garnet is the zodiac stone for those born under the sign Aquarius, and is an Enhancer Strengthener crystal. It has the properties of fire energy and is a talisman of protection.

Physical Properties of Almandine

Chemical FormulaFe3Al2Si3O12
ColourRed, Black
Hardness7.5 - 8.5
Crystal SystemIsometric
Refractive Index1.780 - 1.810
SG4.3
TransparencyTransparent to translucent
Double RefractionNone
LusterVitreous
CleavageNone. May exhibit parting.
Mineral ClassAlmandine (Garnet)

Chrysoberyl

Chrysoberyl

The name chrysoberyl comes from the Greek words chrysos, meaning golden, and beryllos, which refers to its beryllium content. Chrysoberyl has been a prized stone for thousands of years in Asia, as it is believed to provide the wearer with protection from the evil eye. There are three different gem varieties of chrysoberyl. Each of these stones is chemically alike, but optically very different, each one having a unique and beautiful feature of its own. The pale yellow green variety of chrysoberyl came from Brazil, and was known as chrysolite. It was popular in Spanish and Portugese jewelry in the 18th and 19th centuries. This stone displays an exceptional brilliance. Chrysoberyl is the third-hardest frequently encountered natural gemstone and lies at 8.5 on the hardness scale, between corundum and topaz.
Like the eye of a sleek feline predator, the chrysoberyl cat's eye winks at the astonished observer – a real miracle of Nature! That's why only this attractive gemstone has the right to the short, fitting name of "cat's eye". This gem is really something special with its narrow, bright band of light on a shimmering golden background, which seems to glide magically across the surface when the stone is moved.

Often, the name chrysoberyl is spoken in the same breath as that of the beryl group, the most well known representatives of which include the emerald and the aquamarine. The name 'chrysoberyl' comes from the Greek and means 'gold-coloured beryl'. In spite of its name, however, it is not actually a beryl at all. Together with alexandrite, chrysoberyl forms an independent gemstone category, in which the former, which appears to change its colour, is regarded as the more attractive representative, though in fact it is quite definitely the chrysoberyl cat's eye which is entitled to stake that claim.
From a mineralogical point of view, chrysoberyls are aluminium oxide containing beryllium, and thus actually have little in common with the beryls, which belong to the silicate family. Indeed, with their excellent hardness of 8.5 on the Mohs scale, they are clearly superior to the beryls. The popular chrysoberyls come in many nuances between lemon and greenish yellow, and in honey colours and shades from mint green to brownish green, and are mostly found in the gemstone deposits of Brazil, Sri Lanka or East Africa.

Popular Chrysoberyl

Today however, the most popular varieties of chrysoberyl are cat’s eye and alexandrite. Alexandrite, which is a very durable and rare stone, displays a beautiful color change. In the daylight, it is green, but under incandescent light, it changes to a red, mauve, or brown color. It has been said that alexandrite was named after czar Alexander II, as it was discovered on the czar’s birthday in 1830, in the Ural Mountains. Cat’s eye, which is also known as cymophane, contains many parallel, featherlike fluid inclusions or needle like inclusions of rutile. These inclusions, when cut as cabochons, display a white line across the yellowish gray stone. Chrysoberyl is a beryllium aluminum oxide. It is a very hard, durable stone, rating an 8.5 on the hardness scale. In fact, chrysoberyl is exceeded in hardness only by diamonds and corundum. Chrysoberyl has a vitreous luster and occurs in a wide range of colors, from green, to greenish yellow, yellow and brown. When cut well, gems are quite brilliant, but lack fire.
Alexandrite’s color change is caused by small amounts of iron or chromium. Alexandrite is also strongly pleochroic, appearing green, red, orange or yellow when viewed from different directions. Cat’s eye on the other hand, displays no pleochroism. The stone ranges in color from a honey yellow or honey brown color, to a yellowish green or almost emerald green. The most highly prized cat’s eye color however, is a light golden brown. Cat’s eye has a lovely velvety, silk like texture and is different than the common quartz variety of cat’s eye, which is brown and called tiger’s eye. Tiger’s eye is much weaker in color than cat’s eye.