mineral

Polished black stone, likely hematite

Hematite (iron(III) oxide, Fe₂O₃), possibly black obsidian or another polished iron-rich mineral

AI-generated identification · may be incorrect

Smooth, rounded, highly polished dark gray-black surface with metallic to submetallic luster; hematite hardness 5–6.5 Mohs, trigonal crystal structure, no distinct cleavage, and specific gravity about 5.3. The image alone cannot distinguish it confidently from obsidian or black jasper.

Identified September 18, 2026More mineral →

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Physical properties

Formation & geological history

Hematite forms through oxidation in sedimentary, hydrothermal, or metamorphic environments; major deposits range from Precambrian banded-iron formations to younger iron-rich rocks. If obsidian, it is volcanic glass formed by rapidly cooled silica-rich lava.

Uses & applications

Used as an iron ore, pigment, and ornamental or jewelry stone; polished hematite beads and palm stones are common. Obsidian is used for carvings, tools, and jewelry.

Geological facts

A simple streak test is especially diagnostic: hematite leaves a red-to-reddish-brown streak on unglazed porcelain, while obsidian leaves little or no streak. Hematite is strongly dense and may feel unusually heavy for its size.

Field identification & locations

Test streak, weight, and magnetism; hematite may be weakly magnetic after heating, whereas obsidian commonly shows conchoidal fracture. Common sources include Brazil, Australia, South Africa, and the United States.