Friday, 25 November 2016

Ametrine Gemstone

What is Ametrine?

Ametrine also known as Trystine or by it’s trade name Bolivianite, Ametrine is a naturally occurring variety of quartz. It is a “mixture” of Amethyst and Citrine with zones of purple and of yellow or orange, but yet being a crystal of it’s own volition it is not just a mixture but a shade of it’s two cousins. Most commercially available Ametrine is found in the mines of Bolivia, although there have been some deposits found in Brazil as well as India.
The colouring is due to differing oxidation of iron states within the crystal itself, which occurs due to a temperature gradient across the crystal during the time of it’s formation. In order for the Iron to produce both colours within the same crystal, very specific conditions must be present. Not only must there be two separate temperature conditions, they must also remain stable within the entire growth process of the crystal, which is an incredible feat indeed.
Geologists have theorized that within the Anahi mine, just the specific type of heat was flowing in the right direction across a portion of the crystal to create just enough heat to create the perfect balance of heat and cool for the Ametrines to be formed. If the heat would have been any degree higher or lower these lovelies would have become either Amethyst or Citrines. It is told that there are only two places on the planet with this specific heat index to create Ametrine gemstones, the original mine in Bolivia as well as the Hyderabad mine in India.
The Anahi Mine is in a dolomitic limestone of the Murcielago Group, a sequence of limestones up to 1500 feet thick that dip to the southwest in the area of the mine. Some zones within the Murcielago Group are heavily silicified, causing them to resist weathering and stand up above the surrounding Pantanal lowlands as prominent north-south-trending ridges. The Anahi Mine is in a ridge at a location where the dolomitic limestone is faulted and silicified. Most of the mining activity is done underground, with a small amount of production at the surface. 
Hydrothermal activity has facilitated the growth of quartz within fractures and vugs of the dolomitic limestone. The walls of these openings are often covered with a thick layer of massive quartz with euhedral quartz crystals growing inwards towards the centre of the cavities. Some of these are crystals of ametrine; many have been etched by later hydrothermal activity.

What Gives Ametrine Its Colour?

The colours of amethyst and citrine are produced by iron impurities with different oxidation states within the quartz. Purple is thought to be produced by Fe3+ that is oxidized to Fe4+ by natural radiation emitted by the decay of potassium-40 in nearby rocks. The golden-yellow is thought to be produced by Fe3+.
If a well-formed ametrine crystal is sawn perpendicular to the c-axis, the colour zones of amethyst and citrine often form a geometric pattern that radiates outwards from the c-axis like the pieces of a pie. Straight-line contacts separate zones of amethyst from zones of citrine. This pattern is formed by Brazil law twinning in which two quartz crystals of different colour are intergrown to form the bicolour gemstone. It is very different from the bicolour zones of a tourmaline crystal which form by sequential crystallisation.

History of Ametrine

According to legend, the Ayoreo Indian tribe of eastern Bolivia knew about the bicolour quartz crystals over 500 years ago. Perhaps the earliest formal documentation of natural quartz crystals with zonal colouring of purple and yellow is in a 1925 issue of American Mineralogist. These were basal sections of quartz crystals with colour sectors alternating between purple and yellow. 
Reports of a quartz gemstone of mixed purple and yellow colour being produced anywhere in the world begin in the 1960s from vague localities in Brazil, Bolivia, and Uruguay. Because the material was not attributed to a specific mine, some people believed it was produced synthetically, produced by treating amethyst, or mined illicitly. 
In 1989, changes to Bolivian mining laws allowed gemstone mining in eastern Bolivia, and a company, Minerales y Metales del Oriente S.R.L., obtained exclusive mining rights to a few thousand acres. Their property included a mine location with evidence of a long history of illicit mining. To establish credibility in the gemstone trade, the company invited geologists and gemologists to the mine and allowed them to confirm for themselves that the ametrine and citrine produced there were natural.
Today, their Anahi Mine is the world's only important commercial source of natural ametrine and anahite (a clear variety of quartz with a very light tint of lilac). The mine also produces amethyst, citrine, and bicolour materials that are a combination of amethyst and clear quartz (bicolour amethyst) or citrine and clear quartz (bicolor citrine).

Ametrine Gemstones

A crystal containing both amethyst and citrine in contact with one another can be called "ametrine." These crystals usually contain zones of clear quartz, amethyst, and citrine. When these crystals are cut into pieces that are appropriately sized for faceting gemstones, only a portion of the stones will be ametrine. The remainder will be amethyst, citrine, and clear quartz. This is why the Anahi Mine produces a variety of gem materials and why the amount of ametrine produced is limited.
Some of the early people involved in illicit production from the Anahi mine site were intent to produce amethyst and citrine. The novelty of a bicolour gemstone began when some lapidaries, inspired by bicolour tourmaline, began producing emerald-cut stones that were 50% amethyst and 50% citrine with the colour boundary oriented perpendicular to the table of the stone. These stones were very attractive and desirable to people who saw them. The bicolour material then became a focus of production.
When Minerales y Metales del Oriente S.R.L. took over the mine, much of the production was being sold as cutting rough and mineral specimens. Since then the owner has worked to diversify revenue by developing the staff and facilities needed to cut the stones, design jewellery, manufacture jewellery, and market the rough, the loose stones, and finished jewellery. Now a large portion of the world's ametrine gemstones are taken from the Earth and delivered to the end consumer through a few related companies located in Bolivia. 
New methods of cutting have been developed to make maximum use of a finite ametrine resource. Some stones are still cut in the traditional emerald cut with a 50/50 amethyst/citrine split. Others are cut into "blended ametrine" that has random or planned patches of amethyst and citrine. These stones are cut in orientations that allow light penetrating the stone to pass through zones of purple amethyst and golden-yellow citrine. This can yield beautiful stones with face-up colours that include peach, magenta, and orange.

Ametrine Healing Properties

Wearing Ametrine jewellery may be helpful to you, and may provide you with ways to let go of stress, as they help to create peace and inner harmony.
It is an extremely useful tool for those in the healing profession to utilise. As well it is also very helpful for the average person to use, to work on themselves at home.
If you are working on losing weight, the energy of one of these quartz crystals will aid you. Like Amethyst crystals, it is useful if you have addictions.
It will to help you in letting go of the compulsions associated with them. 
It will clear stress and tension from the head, and will bring excess energy down into the physical for use or release.
Its Citrine energy will enhance your will, and the Amethyst vibration helps you to break self-defeating habits, that may be holding you back. 
Their energy is also said to alleviate depression, anxiety and stress. 
The Citrine Crystal vibration helps you to boost your creativity, and its connection with the crown, the highest chakra in the body may assist psychic artists in their work.

Physical properties of Ametrine

Chemical FormulaSiO2
ColourYellow, Purple, Multicolored
Hardness7
Crystal SystemHexagonal
Refractive Index1.54 - 1.55
SG2.63 - 2.65
TransparencyTransparent
Double Refraction.009
LusterVitreous
CleavageIndiscernible
Mineral ClassQuartz