Pyrite in Quartz
Quartz var. Milky Quartz with Pyrite Inclusions · Mineral Specimen and Collector Mineral
Crystal System
Trigonal (Quartz) / Cubic (Pyrite); massive or amorphous crystalline habit as a specimen
Mineral Group
Silicates (Tectosilicate subgroup) associated with Sulfide minerals
Chemical Formula
SiO2 (Quartz matrix) with FeS2 (Pyrite inclusions)
Formation Process
Hydrothermal formation where silica-rich fluids deposit quartz, often trapping iron sulfide (pyrite) crystals during the crystallization process at moderate temperatures and pressures.
About This Crystal
An opaque to translucent milky-grey to white quartz matrix embedded with small, brassy-yellow metallic specks and crystals of pyrite. The specimen has an irregular, broken rock shape with a vitreous to greasy luster on the quartz and bright metallic luster on the pyrite inclusions.
Physical Characteristics
Color ranges from milky white and grey to brassy yellow; white streak; no true cleavage in quartz, conchoidal fracture; specific gravity around 2.65 for quartz and 5.0 for pyrite; brittle tenacity; non-magnetic.
Optical Properties
Singly or doubly refractive depending on the quartz orientation; uniaxial positive birefringence; opaque pyrite inclusions show strong metallic reflection with no transmission of light.
Hardness & Durability
Origin Region
Worldwide distribution; major sources include Peru, USA (Colorado), Brazil, and Spain. Forms in hydrothermal veins and pegmatites.
Hardness & Durability
Mohs hardness of 7 for the quartz host, making it quite durable, though the included pyrite is softer at 6-6.5; moderate toughness; resistant to scratching but sensitive to hydrofluoric acid.
Care & Maintenance
Safe to clean with warm soapy water; avoid harsh chemical cleaners and prolonged exposure to direct sunlight if treated, though natural quartz is stable; store separately from softer gemstones to prevent scratching.
Rarity & Value
Common to uncommon depending on aesthetic quality and crystal definition; value depends on the clarity of the quartz and the size and distribution of the pyrite crystals; typically ranges from inexpensive to moderately priced for mineral specimens.
Special Characteristics
Features metallic pyrite inclusions embedded within a translucent quartz host, creating a striking contrast between the glassy silicates and the golden, brassy sulfide specks often referred to as 'Fool's Gold'.
Lore & History
Pyrite in quartz is traditionally believed to combine the manifestation and energy-shielding properties of pyrite with the amplification properties of quartz. Historically, pyrite was used by ancient civilizations for sparking fire and as a decorative stone, while quartz has long been used in human culture for tools, ornamentation, and spiritual practices.