mineral
Tumbled black stone, likely black tourmaline (schorl)
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectOpaque black with a polished, vitreous-to-submetallic luster; tourmaline is trigonal, Mohs hardness 7–7.5, and has poor cleavage. The photo does not show enough detail to confirm the identification.
Identified More mineral →
Explore Tumbled black stone, likely black tourmaline (schorl) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Opaque black with a polished, vitreous-to-submetallic luster; tourmaline is trigonal, Mohs hardness 7–7.5, and has poor cleavage. The photo does not show enough detail to confirm the identification.
Formation & geological history
Black tourmaline forms in boron-rich granitic pegmatites and metamorphic rocks, commonly during late-stage crystallization. Such deposits occur across a wide range of geological ages.
Uses & applications
Tumbled pieces are used for jewelry, ornament, and mineral collecting; tourmaline is also valued as a gemstone.
Geological facts
Schorl is the most common tourmaline species and often grows as strongly striated, elongated crystals before being cut or tumbled.
Field identification & locations
A tumbled specimen may have its diagnostic crystal shape and striations removed; confirm by hardness and, ideally, mineral testing. Tourmaline is found in pegmatites worldwide, including Brazil, Africa, and the United States.
More like this
Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral