mineral
Quartz with Pyrite inclusions
Silicon Dioxide (SiO2) with Iron Sulfide (FeS2) inclusions
Hardness: 7 (Quartz) and 6-6.5 (Pyrite). Color: Clear to milky white with metallic brassy-yellow specks. Luster: Vitreous (glassy) for quartz, metallic for pyrite. Crystal structure: Trigonal (Quartz) and Cubic (Pyrite). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65 for Quartz.
- Hardness
- 7 (Quartz) and 6-6
- Color
- Clear to milky white with metallic brassy-yellow specks
- Luster
- Vitreous (glassy) for quartz, metallic for pyrite
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Physical properties
Hardness: 7 (Quartz) and 6-6.5 (Pyrite). Color: Clear to milky white with metallic brassy-yellow specks. Luster: Vitreous (glassy) for quartz, metallic for pyrite. Crystal structure: Trigonal (Quartz) and Cubic (Pyrite). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65 for Quartz.
Formation & geological history
Formed through hydrothermal processes where silica-rich fluids cool and crystallize in veins or pockets of igneous and metamorphic rocks. Pyrite crystals form simultaneously or prior to the quartz crystal growth. These can be found in formations ranging from Precambrian to more recent geological eras.
Uses & applications
Primarily used as collector specimens and in jewelry as 'fool's gold' in quartz. Industrial quartz is used in glassmaking and electronics (piezoelectric properties), though clear specimens with metallic inclusions are usually reserved for the lapidary arts.
Geological facts
Pyrite is nicknamed 'Fool's Gold' due to its metallic luster and brassy hue which often deceived early prospectors. When struck against steel, pyrite can create sparks, hence its name which comes from the Greek word 'pyr' meaning fire.
Field identification & locations
Identify by quartz's ability to scratch glass and its lack of cleavage. Brassy yellow metallic flecks with a greenish-black streak (if powdered) identify the pyrite. Commonly found in mountainous regions globally, particularly in Brazil, the USA (Arkansas), and the Alps.
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