Pegmatite
“Home of giant crystals”
Igneous
Pegmatite is an extremely coarse-grained igneous rock that forms in the final stages of magma crystallization, when water-rich residual fluids allow crystals to grow to enormous sizes. It's the primary source of lithium, rare earth elements, and gemstones.
Composition
quartz, feldspar, mica, tourmaline, beryl, spodumene (variable)
Where Found
Black Hills (South Dakota, USA), Minas Gerais (Brazil), Hagendorf (Germany), Afghanistan
Mohs Hardness
6-7 (varies by mineral)
Fun Fact
The Etta Mine in South Dakota produced a single spodumene crystal from pegmatite that was over 14 meters long and weighed about 37 tonnes.
Test Your Knowledge
Why are pegmatites the primary global source of lithium, beryllium, and tantalum?
Related Specimens
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