mineral
Rutile in matrix (likely quartz-bearing specimen)
Rutile, titanium dioxide (TiO₂), with quartz and possibly chlorite/mica matrix
AI-generated identification · may be incorrectBlack to reddish-black, submetallic to adamantine luster; rutile is tetragonal and commonly forms prismatic crystals or knee twins. Hardness 6–6.5, specific gravity about 4.2–4.3, with imperfect cleavage; the pale gray material appears quartz or mica.
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Physical properties
Black to reddish-black, submetallic to adamantine luster; rutile is tetragonal and commonly forms prismatic crystals or knee twins. Hardness 6–6.5, specific gravity about 4.2–4.3, with imperfect cleavage; the pale gray material appears quartz or mica.
Formation & geological history
Forms in high-temperature hydrothermal veins and metamorphic rocks, often with quartz. Rutile crystallized during metamorphism or vein formation; an exact geological age cannot be determined from the photograph.
Uses & applications
Rutile is an important titanium ore and produces titanium dioxide pigment; attractive crystals are collected. Quartz-bearing pieces are mainly mineral specimens rather than jewelry-grade material.
Geological facts
The strongly reflective, black prismatic crystals and apparent twinning are characteristic of rutile. Similar-looking black minerals include schorl tourmaline and hematite, so chemical or optical testing may be needed for certainty.
Field identification & locations
Look for dense black, sharply terminated tetragonal crystals, often knee-twinned, embedded in quartz or mica. Common localities include Graves Mountain, Georgia; the Swiss Alps; Brazil; Madagascar; and Norway.
