metamorphic
Quartzite with vugs/druzy quartz
Crystalline Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: White to grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (hexagonal system); No cleavage, conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- White to grayish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (hexagonal system); No cleavage, conchoidal fracture.
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. The vugs (cavities) visible may contain later-stage mineral precipitates or results of hydrothermal fluids. Usually formed during mountain-building events in the Precambrian or Paleozoic eras.
Uses & applications
Used in construction for road ballast, floor tiles, and stone walls. High-purity quartzite is used to produce glass, silicon metal, and ferrosilicon. This specific specimen has interest for amateur geologists due to its unique secondary mineralization.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in mountainous areas, forming prominent ridges. Pure quartzite is usually white or gray, but it can be pink or red if it contains iron oxides.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in riverbeds or near mountain ranges where tectonic activity has occurred. This specimen shows vugs which are common in secondary hydrothermal activity areas.
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