igneous
Tourmaline-bearing pegmatite (likely black schorl in a pale quartz/feldspar matrix)
Schorl tourmaline, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄, with quartz and feldspar
AI-generated identification · may be incorrectThe specimen appears to contain a black, lustrous mineral in a white-to-cream coarse-grained matrix. Schorl has Mohs hardness 7–7.5 and a trigonal crystal structure; quartz is hardness 7. Identification from the photo is provisional.
Identified More igneous →
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Physical properties
The specimen appears to contain a black, lustrous mineral in a white-to-cream coarse-grained matrix. Schorl has Mohs hardness 7–7.5 and a trigonal crystal structure; quartz is hardness 7. Identification from the photo is provisional.
Formation & geological history
Likely crystallized slowly from boron-rich residual magma in a granitic pegmatite, often during the late stages of granite formation. Its precise age and locality cannot be determined from the image.
Uses & applications
Tourmaline is collected as a mineral specimen and sometimes cut for jewelry; quartz and feldspar are common industrial minerals. This rough piece is more likely a collector specimen than gem material.
Geological facts
Schorl is the most common tourmaline species and is typically black because of its iron content. Pegmatites can host exceptionally large crystals.
Field identification & locations
Look for black, elongated, striated tourmaline crystals embedded in coarse quartz and feldspar; confirm with crystal shape or testing, since other dark minerals can look similar. Pegmatites occur worldwide.
