igneous
Quartz-rich pegmatite with iron-stained quartz
Quartz (SiO₂) in granitic pegmatite, likely with feldspar and iron-oxide staining
AI-generated identification · may be incorrectWhite to gray, coarse-grained, translucent quartz with glassy to greasy luster; associated pale feldspar and yellow-brown iron oxides. Quartz hardness is Mohs 7, with no cleavage; feldspar is Mohs 6–6.5 and cleaves readily.
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Physical properties
White to gray, coarse-grained, translucent quartz with glassy to greasy luster; associated pale feldspar and yellow-brown iron oxides. Quartz hardness is Mohs 7, with no cleavage; feldspar is Mohs 6–6.5 and cleaves readily.
Formation & geological history
Likely formed from the final, water-rich melt of a slowly cooling granite intrusion, allowing exceptionally large crystals to grow. Pegmatites are generally Precambrian to Cenozoic in age, depending on locality.
Uses & applications
Used as a collector specimen; quartz and feldspar from pegmatites are also used in glass, ceramics, abrasives, and industrial mineral products.
Geological facts
The coarse crystals and contrasting rusty staining are characteristic of pegmatitic material. The yellow-brown areas may be limonite/goethite coating or weathering products.
Field identification & locations
Identify by very large interlocking crystals, hardness sufficient to scratch glass, and quartz lacking cleavage; feldspar breaks along flat cleavage planes. Common in granite- and metamorphic-belt regions worldwide.
