igneous
Tourmaline-bearing pegmatite
Quartz–feldspar pegmatite with black schorl tourmaline; minor mica likely present
AI-generated identification · may be incorrectCoarse-grained, pale pink to white matrix of quartz and feldspar with embedded black, striated tourmaline crystals. Quartz hardness 7, feldspar 6–6.5, schorl tourmaline 7–7.5; generally vitreous to pearly luster, with irregular fracture and locally visible cleavage in feldspar/mica.
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Physical properties
Coarse-grained, pale pink to white matrix of quartz and feldspar with embedded black, striated tourmaline crystals. Quartz hardness 7, feldspar 6–6.5, schorl tourmaline 7–7.5; generally vitreous to pearly luster, with irregular fracture and locally visible cleavage in feldspar/mica.
Formation & geological history
Formed when volatile-rich granitic magma cooled slowly in a late-stage pegmatite vein, allowing exceptionally large crystals to grow. Commonly Cretaceous to Precambrian depending on locality; the exact age cannot be determined from the image.
Uses & applications
Collected as an attractive mineral specimen; similar pegmatites supply feldspar, quartz, mica, lithium minerals, and gem tourmaline. Usually not used as construction stone because of its coarse, uneven texture.
Geological facts
Black schorl is the most common tourmaline variety and commonly forms radiating or prismatic crystals in granitic pegmatites. The pink coloration may reflect potassium feldspar, iron staining, or pale lithium-rich minerals.
Field identification & locations
Look for sharply prismatic, longitudinally striated black tourmaline contrasting with blocky feldspar and glassy quartz. Common sources include Brazil, Afghanistan, Pakistan, Madagascar, the United States, and parts of Europe.
