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 Home / Gem Library / Natural Gemstones / Chalcedony November 21, 2017  


Natural Chalcedony
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There are 60 Chalcedony(s) available at Multicolour.com


The name chalcedony is applied to any fine grained quartz with a fibrous or crypto- crystalline microstructure. It often displays some kind of distinctive banding. The name agate is used for the sub variety of chalcedony which displays distinctive banding with successive layers differing in color and degree of translucency.


Known Facts
Color Key: grayish, purple, white, green, blue, lavender, yellow, brown.
Refractive Index: 1.530 - 1.539
Chemical Composition: SiO2
Hardness: 6.5
Density: 2.57 2.64
Crystal Group: Hexagonal
Ocurrence: Brazil, U.SA. Germany, India, Uruguay, Austarlia, Egypt, Italy, Scotland, South Africa, Namibia, Madagascar, Mexico, Tanzania, and many other localities throughout the world.

The individual fibers of chalcedony and its subvarieties are not physically separable; they occur as parallel or near parallel aggregates or as spherules. The fiber direction is perpendicular to the layering while the banding is parallel to the free surface or cavity in which the chalcedony occurs.

The hardness of chalcedony is variable around 6.5; somewhat lower than that of more coarsely crystallized quartz which has a hardness of 7. The specific gravity also varies according to porosity, water content, and the presence of other substances. The normal range is 2.57 2.64. Chalcedony is about 90 99% SiO2. Brown and reddish varieties are higher in Fe2O3.

Chalcedony fractures easily across the banding to give a splintery surface with a waxy luster. Most chalcedony is somewhat pale and grayish in appearance.

Chalcedony is deposited in a variety of environments and deposition is commonly at low temperatures. Light colored material is often found as a late hydrothermal deposit or an alteration product in acidic or basic igneous rocks, tuffs and breccias. It is very common as crusts of vein or cavity fillings.

The most prized of the chalcedonies are the translucent green stones known as chrysoprase and the brown iridescent and colorful stones known as fire agates. Other important kinds of chalcedony include bloodstone, lace agate, sard, iris agate, onyx, and carnelian.


Illustrations
Chalcedony Chalcedony Chalcedony Chalcedony
Check our Top, Largest, Smallest or Latest Chalcedony's.


Chalcedony Stats/
Popularity Index: 4835520hits
Total Items: 60items
Total Weight: CTS 2500.20
Cheapest: USD 1.09
Most Expensive: USD 90.88
Largest: CTS 60.18
Smallest: CTS 0.50
Last Added: 11/07/17 09:22:50

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