Nephrite jade
Chemical composition: a fibrous variety of the amphibole mineral series actinolite to tremolite, usually closer to actinolite.
Colour: green, black, brown, beige (mutton-fat jade). Usually darker and less intense colors than those of jadeite.
R.I. : 1.62.
Hardness: 6-6.5. Extremely tough, except when its composition approaches that of tremolite.
Crystal structure: monoclinic, usually massive.
Specific gravity: 2.9-3.0.
Sources: many sources, including British Columbia, Chinese Turkestan,Taiwan, New Zealand, Wyoming, Lake Baikal and California.
