igneous
Quartz-rich granitic pegmatite
Pegmatite, composed mainly of quartz (SiO₂), feldspar, and minor mica or iron-oxide minerals
AI-generated identification · may be incorrectLight cream to pink-white, coarse crystalline texture, vitreous to pearly luster, and irregular fracture; quartz hardness is 7 Mohs, while feldspar is about 6. The specimen appears weathered and iron-stained, with no obvious cleavage visible at this scale.
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Physical properties
Light cream to pink-white, coarse crystalline texture, vitreous to pearly luster, and irregular fracture; quartz hardness is 7 Mohs, while feldspar is about 6. The specimen appears weathered and iron-stained, with no obvious cleavage visible at this scale.
Formation & geological history
Formed when the final, water-rich melt in a granite intrusion cooled slowly, allowing oversized crystals to grow. Pegmatites are generally Precambrian to Phanerozoic and occur in veins or pods cutting older granitic and metamorphic rocks.
Uses & applications
Used locally as decorative stone and aggregate; pegmatites are important sources of feldspar, quartz, mica, lithium, beryllium, tantalum, and rare gemstones. This small irregular piece has mainly educational or modest collecting value.
Geological facts
The large interlocking crystals are characteristic of pegmatites, though the image does not show a diagnostic gem mineral. Pink coloration commonly comes from potassium feldspar, while green, brown, or reddish patches may reflect mica or iron oxides.
Field identification & locations
Look for very coarse interlocking crystals, glassy quartz, blocky feldspar cleavage, and flaky mica. Common worldwide near granitic terrains, including Brazil, Madagascar, the United States, and Canada; definitive identification may require a fresh surface or hardness test.
