Herkimer Diamond (Quartz)
Quartz (Variety: Herkimer Diamond) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal/Hexagonal; typically occurs as doubly terminated rhombohedral prisms
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide) with organic hydrocarbon inclusions (anthraxolite)
Formation Process
Hydrothermal; formed in cavities of host rock (dolostone) roughly 500 million years ago
About This Crystal
Transparent to translucent, water-clear to smoky, vitreous luster, often containing black flecks
Physical Characteristics
Colorless to pale yellow; White streak; No cleavage; Conchoidal fracture; SG 2.65; Brittle
Optical Properties
Refractive Index 1.544–1.553; Birefringence 0.009; Weak pleochroism; Uniaxial (+) optical sign
Hardness & Durability
Origin Region
Herkimer County, New York, USA; found in Little Falls Dolostone vugs
Hardness & Durability
7.0 on Mohs scale; Good toughness; Very stable and excellent for jewelry use
Care & Maintenance
Wash with warm soapy water; safe for ultrasonic cleaners; avoid extreme thermal shock
Rarity & Value
Uncommon globally but locally abundant in NY; value depends on clarity and seed inclusions
Special Characteristics
Naturally doubly terminated; includes distinctive black anthraxolite inclusions (hydrocarbon)
Lore & History
Discovered in late 18th century; traditionally associated with 'attunement' and third-eye chakra