Chalcedony – Moss Agate

Appearance:

• Chalcedony is microcrystalline or cryptocrystalline quartz; hexagonal (trigonal) crystal system; chemical composition SiO2
• Semitransparent to opaque
• Virtually all colors
• Moss agate or mocha stone – chalcedony with green, black, or brown inclusions that look like moss

Identification:

• Optic Character: AGG
• Refractive Index: 1.535-1.539; 1.53 or 1.54 spot reading
• Birefringence: usually not detectable, but may show .004
• Pleochroism: none
• Ultraviolet Fluorescence: generally inert (LW and SW); some may fluoresce a yellowish green (LW and SW)
• Absorption Spectra: dyed green – vague lines around 645 and 670 nm
• Specific Gravity: 2.60 (+.10,-.05)
• Hardness: 6 ½  to 7
• Toughness: good

Sources:

• India, US

Stone information is reference from:

• Gem Reference Guide, Published by GIA. ISBN 0-87311-019-6
• Gemstones of the World, Published by Sterling Publishing Co., Inc NY, ISBN 1-4027-4016-6
• Encyclopedia of GEMSTONE, Published by ISHINSHA CO., LTD. ISBN 978-986-251-831-1