metamorphic
Orange Quartzite (Tumbled)
Quartzite (primarily SiO2 with trace Iron Oxide)
Hardness: 7 (Mohs scale); Color: Orange, reddish-brown, or peach; Luster: Vitreous to waxy when polished; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6 - 2.7
- Hardness
- 7 (Mohs scale)
- Color
- Orange, reddish-brown, or peach
- Luster
- Vitreous to waxy when polished
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Physical properties
Hardness: 7 (Mohs scale); Color: Orange, reddish-brown, or peach; Luster: Vitreous to waxy when polished; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. This process recrystallizes the quartz grains into a dense, interlocking mosaic of crystals. Most deposits range from Proterozoic to Paleozoic in age.
Uses & applications
Used widely as decorative stone, in jewelry (lapidary), as railroad ballast, and in construction due to its extreme durability. High-purity quartzite is also used to produce silicon for glass and electronics.
Geological facts
Quartzite is so tough that it often survives erosion better than the mountains it originated from, leading to the formation of 'monadnocks' or resilient ridges. Its orange color typically comes from minute amounts of hematite or limonite staining.
Field identification & locations
Identify by its ability to scratch glass and its grainy, crystalline texture that looks like sandpaper but feels smooth once polished. Commonly found in folded mountain belts like the Appalachians or the Alps. For collectors, look for rounded river-worn pebbles with consistent color.
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