Assignment 25 - Lapis Lazuli, Turquoise, and Other Opaque Gems Flashcards
What mineral produces lapis lazuli’s best color?
Lazurite produces lapis lazuli’s prized royal blue color.
How is lapis rough extracted from the remote cliffs of Afghanistan?
The Afghani mines are huge caverns connected by narrow, hot, stuffy passageways. Miners use dynamite to rattle the rough lapis loose from the cave walls.
What are the common lapis treatments?
Lapis might be dyed, impregnated with wax or plastic, or heated and then dyed.
How have political events affected the lapis market?
During the country’s 1984 civil war, the Afghani government sold large quantities of lapis to raise funds to fight the Soviet- backed regime. As a result, huge quantities of lapis rough flooded the global market, and prices dropped.
In the 1990s, civil unrest in the area affected the global market. Supply of lapis lazuli rough from Afghanistan plunged 50 percent because of fighting in the mining area of Badakhshan.
What’s the top color for turquoise?
An intense, uniform, medium blue is turquoise’s most-prized color.
How does porosity affect turquoise value?
Low porosity and fine texture are more valuable in turquoise than high porosity and coarse texture.
What area of the US is one of the largest turquoise producers in the world?
The southwestern US is the world’s largest producer of turquoise, while China’s Hubei Province is the major source of its top color.
How do turquoise treatments affect the gem’s marketability?
Natural turquoise’s porosity, usually a threat to its stability, allows it to accept treatments readily.
Colorless oil or polymer plastic is often used instead of wax.
Turquoise can be dyed to improve its color and make it more even.
A turquoise treatment called the Zachery method makes turquoise less porous without the use of polymers and improves its ability to take a good polish.
Turquoise that contains matrix in thin, web-like patterns.
Spiderweb turquoise
A turquoise imitation made of a mixture of powdered minerals, dyed and bonded with plastic or epoxy resin.
Reconstructed turquoise
A trade term for polymer-impregnated turquoise.
Stabilized turquoise
What makes some translucent to opaque materials suitable for ornamental use?
Poor toughness allows carving and variety of colors adds to the appeal.
What is banded marble?
Onyx Marble, a variety of calcite
Which translucent to opaque gemstones feature a rose-red hue?
Rhodonite
What are some opaque metallic gems?
- Hematite (“Black Diamond”)
- Pyrite (“Fool’s gold”)
