mineral
Quartz (Iron-Stained / Vein Quartz)
Silicon Dioxide (SiO2)
Mohs hardness of 7; vitreous to greasy luster; color range from off-white/milky to yellow-brown due to iron oxide surface staining; conchoidal fracture with no distinct cleavage; trigonal crystal system
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Physical properties
Mohs hardness of 7; vitreous to greasy luster; color range from off-white/milky to yellow-brown due to iron oxide surface staining; conchoidal fracture with no distinct cleavage; trigonal crystal system
Formation & geological history
Formed in hydrothermal veins and pegmatites during cooling of magmatic fluids, as well as metamorphism. Common along riverbeds, stream channels, and mountainous regions worldwide.
Uses & applications
Used industrially as a source of silicon, in glassmaking, optics, electronics, and abrasives. Common raw quartz specimens are also collected by rockhounds.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. The yellow and brownish coating on this piece is limonitic or hematitic iron oxide left behind by weathering groundwater.
Field identification & locations
Identified by its ability to easily scratch glass and steel, its lack of cleavage, and translucent to milky appearance. Very abundant in gravel bars and riverbeds.
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