metamorphic
Orange Quartzite
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: Orange, reddish-brown, and peach, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture, Specific Gravity: 2.63-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Orange, reddish-brown, and peach, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture, Specific Gravity: 2.63-2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize and fuse together. The orange color is typically due to trace amounts of iron oxide (hematite or limonite) included during formation.
Uses & applications
Used as a decorative stone in landscaping, crushed stone for road construction, and occasionally in jewelry as tumbled stones or cabochons. It is also used as a source of silica in glass manufacturing.
Geological facts
Quartzite is so hard that it can scratch steel and glass. In many mountain ranges, quartzite forms the high peaks because it is extremely resistant to chemical and physical weathering compared to surrounding rocks.
Field identification & locations
Identify in the field by its extreme hardness and its sugary, granular texture that sparkles slightly under light. Unlike sandstone, quartzite breaks through the quartz grains rather than around them. Found globally in ancient mountain belts and glacial deposits.
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