igneous
Quartz-rich pegmatite
Pegmatitic granite, chiefly quartz (SiO₂), feldspar, and minor mica/iron-oxide staining
AI-generated identification · may be incorrectCoarse-grained, white to pale gray with rusty brown weathering; vitreous quartz luster and blocky feldspar crystals are visible. Quartz hardness is 7, feldspar 6–6.5; cleavage is absent in quartz but strong in feldspar, and the texture is crystalline and interlocking.
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Physical properties
Coarse-grained, white to pale gray with rusty brown weathering; vitreous quartz luster and blocky feldspar crystals are visible. Quartz hardness is 7, feldspar 6–6.5; cleavage is absent in quartz but strong in feldspar, and the texture is crystalline and interlocking.
Formation & geological history
Formed when the final, water-rich melt in a granitic magma cooled slowly in a dike or vein, allowing exceptionally large crystals to grow. Its precise age cannot be determined from the image; pegmatites range from Precambrian to recent geologic periods.
Uses & applications
Commonly collected as a field specimen; comparable pegmatites may supply feldspar, quartz, mica, lithium, beryllium, or tantalum. Attractive pieces can be used decoratively, though this weathered specimen has limited gemstone value.
Geological facts
The orange-brown coloration is likely limonite/goethite staining along fractures and weathered feldspar. The surrounding angular green-gray fragments suggest a weathered vein or coarse intrusive body.
Field identification & locations
Identify it by unusually coarse interlocking quartz and feldspar, white translucent fracture surfaces, and rusty fracture staining; it is commonly found in granitic terrains and pegmatite dikes. A hand lens and streak, hardness, or acid tests would improve confirmation.
