Moss Agate

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

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