metamorphic
Blue Quartzite (Blue Aventurine)
Silicon Dioxide (SiO2) with inclusions of Dumortierite or Magnesio-riebbeckite
Hardness: 7 on the Mohs scale. Color: Muted blue to grayish-blue. Luster: Vitreous to dull/sugary. Crystal Structure: Trigonal (microcrystalline/granoblastic texture). Cleavage: None (conchoidal to uneven fracture). Specific Gravity: 2.63 - 2.65.
- Hardness
- 7 on the Mohs scale
- Color
- Muted blue to grayish-blue
- Luster
- Vitreous to dull/sugary
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Physical properties
Hardness: 7 on the Mohs scale. Color: Muted blue to grayish-blue. Luster: Vitreous to dull/sugary. Crystal Structure: Trigonal (microcrystalline/granoblastic texture). Cleavage: None (conchoidal to uneven fracture). Specific Gravity: 2.63 - 2.65.
Formation & geological history
Formed when quartz-rich sandstone undergoes intense heat and pressure during regional metamorphism. The distinct blue hue is typically caused by fibrous inclusions of minerals like dumortierite, crocidolite, or magnesio-riebbeckite within the quartz matrix.
Uses & applications
Used primarily as decorative stone, lapidary material for carving, tumbled gemstones, beadwork, landscape accents, and architectural dimension stone.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering. When pure quartz sandstone metamorphoses into quartzite, individual quartz grains recrystallize, interlocking like puzzle pieces to create a dense, sugary-textured rock.
Field identification & locations
Identified by its sugary granular texture, hardness (scratches glass easily), lack of acid reaction, and distinct grayish-blue color. Commonly found in Brazil, India, Russia, and Parts of the United States.
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