紫水晶

Description:

The variety of the mineral quartz; hexagonal (trigonal) crystal system. Major Sources: Brazil, Uruguay, Namibia.

Appearance:

• Transparent; material used for beads and carvings may be translucent 
• Bluish purple to purple to reddish purple; often shows a slight shift in hue under different lighting

Identification:

Optic Character: DR, uniaxial positive 
Refractive Index: 1.544-1.553 (very constant)
Cause of Color: color centers involving iron impurities and irradiation
Hardness: 7 ; Toughness: good

Stone Information 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
https://www.gemdat.org/gem-198.html
https://www.mindat.org/min-198.html