Crystal

Appearance:

• Quartz species; hexagonal (trigonal) crystal system; chemical composition SiO2
• Rock crystal – transparent colorless

Identification:

• Optic Character: DR uniaxial positive or AGG (depending on variety)
• Refractive Index: 1.544-1.553 (very constant)
• Birefringence: .009 (may not be detectable in aggregate varieties) Dispersion: .013
• Pleochroism: none
• Specific Gravity: 2.66 (+.03.-.02)
• Polish Luster: vitreous Fracture: conchoidal to uneven or granular (in aggregates)
• Luster: vitreous
• Cleavage: none
• Identifying Characteristics: 2-phase, and 3-phase lusions, negative crystals, may show bull’s-eye or Airy’s spiral optic figure.
• Hardness: 7
• Toughness: good. 

Birthstone Designation(s):

• Rock crystal – Monday

Major Source:

• Brazil, Madagascar, US, Alps.

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