metamorphic
Yellow Quartzite (Iron-stained)
Quartzite (primarily SiO2 with Fe2O3 staining)
Hardness: 7 on Mohs scale; Color: Yellow, golden brown, or tan; Luster: Vitreous to waxy (when wet); Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Yellow, golden brown, or tan
- Luster
- Vitreous to waxy (when wet)
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellow, golden brown, or tan; Luster: Vitreous to waxy (when wet); Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. Under intense heat and pressure, individual quartz grains recrystallize and fuse together. The yellow color is typically caused by iron oxide (limonite or goethite) staining the surface or filling microscopic cracks.
Uses & applications
Used primarily as decorative stone, in landscaping, as a construction aggregate, and occasionally for lapidary work (cabochons) due to its hardness and durability.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, unlike sandstone. It is often more resistant to weathering than the surrounding rock, leading it to form prominent ridges and hilltops.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass and steel) and its granular, sugary texture. Look for the absence of visible pores which distinguishes it from sandstone. This specimen is water-worn, likely found in a riverbed or on a beach.
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