Kariba Minerals Ltd - Zambia amethyst
 

AMETHYST GUIDE

     
 

Appreciation for Amethyst

Enthusiasts who appreciate quartz's diverse family of gems often single out amethyst as the most significant variety of the quartz mineral. Amethyst has been used in personal adornment for centuries. often sought out by royalty or important members of the clergy.

In Medieval Europe particularly, the colour purple was worn in rare dyed textiles that could only be afforded by the very wealthy. Amethyst’s bold purple colour, and rare reddish flashes. coupled with the fact that only a few mines for it existed in ancient time s, further contributed to its selection as a "royal gem." Important amethysts feature prominently in British regalia. The name amethyst has a peculiar derivation. It comes from the Greek word amethystos which translates to "not drunk."An ancient belief that amethyst protected its wearer from inebriation (even following copious consumption of alcohol) consequently made the gem highly desirable by those so inclined.

Amethyst on the Calendar
Amethyst is the Birthstone for February.
It is also considered to be a 6th anniversary gem.

What an amethyst is
Amethyst is a variety of quartz that grows in a hexagonal crystal system and has the following chemical composition : SiOz.

Colour(s): Transparent to translucent lilac to purple through bluish purple, with a reddish purple colour-shift that is sometimes visible in incandescent light. In ametrine. a unique form of quartz mined from a single locality in Bolivia, the colours are both yellow and purple in areas of zoning. Such gems are sometimes cut in a way that mixes the colours, and at other times to show the division of colours.

Refractive Index: 1.544 to 1.533
Birefringence: 0.009
Specific Gravity: 2.66 (+0.03. -0.02)
Cause(s) of colour: are colour centres in quartz, natural irradiation in the mine. combined with traces of iron.

Hardness: 7 on the Mohs Hardness Scale.

Internal identifying characteristics
Amethysts often contain areas of colour next to areas that have no colour- called colour zoning. Amethyst, which has a hydrothermal geologic formation, often has liquid inclusions containing solids and gases, so-called two and three phase industons. Inclusions of other minerals such as rutile and hematite sometimes can be found in amethyst as well.

Amethyst's treatments
Amethyst is sometimes subject to heat treatment, which in a controlled environment may cause overly dark amethysts to be lightened. Occasionally heating amethyst from some sources may turn them yellow. Heating may remove a smoky component in some amethysts.

 

 

Collector amethysts

Collectors of amethyst look for depth of the purple colour with red flashes if the gem is cut conventionally. Many famous lapidaries (CUller s) work with amethysts to make unusual carvings or cuts which are also highly prized. Because the bi-coloured ametrine comes from only one mine in the world, it is sometimes collected if the depth of colour and the division of colour is strong or if it has been skillfully or cleverly carved.

Amethyst localities
Russia is considered the "classic" source For amethysts because that is where it came from before the discovery of amethysts in the New World. "Uralian" or "Siberian" amethysts, at their best, exhibit deep reddish purple to purple red colours. The discoveries of amethysts in Zambia and Brazil changed the dynamics of the market because much larger volumes of material became available in the 20th Century.

Some important localities in the United States. particularly in Arizona are also contributing supplies of amethyst to world markets.

The cutting and care of amethysts
Amethyst - once considered rare - today has thankfully become one of the world's most plentiful, and thus democratic of gems. It can be found in many sizes. Amethyst is offered in many different kinds of cuts and carvings. Amethyst is also fairly resilient and can be worn extensively. Care should be taken not to knock the gem during use, as small fissures or cracks may develop especially along facet junctions. It can be cleaned with warm, sudsy water or a dampened cloth. Some amethysts may lighten in tone over time upon prolonged exposure to bright light.

 

kariba amethyst

Source: CIBJO Retailers' Reference Guide, july 2009