Key properties
| Chemical formula | Fe2O3 |
| Crystal system | Trigonal |
| Mohs hardness | 5.5-6.5 |
| Toughness | Fair to good (brittle in crystalline material; massive material wears well) |
| Refractive index | 2.870-3.220 |
| Birefringence | 0.2800 |
| Optic character | Uniaxial negative; opaque to transmitted light in gem material (-) |
| Specific gravity | 4.90-5.30 |
| Cleavage | None |
| Fracture | Subconchoidal to uneven, splintery or granular |
| Habit | Botryoidal 'kidney ore' (the classic gem material), massive, platy 'specularite', and thick tabular crystals with a metallic 'iron rose' look |
| Lustre | Metallic to splendent (specularite); dull earthy in weathered material; polish: Bright metallic, mirror-like |
| UV fluorescence | Inert |
| Pleochroism | None visible in opaque material (crystallographically O brownish-red / E yellowish-red) |
| Cause of colour | Grey-black from intense absorption across the visible spectrum by electronic transitions in iron(III) oxide; the red 'blood' tone shows in the streak and thin splinters |
| Typical inclusions | Red-brown internal tones seen at thin edges; intergrowth with martite after magnetite in some deposits |
| Stability | Stable to light and everyday chemicals; soluble with difficulty in hot concentrated hydrochloric acid; may become magnetic after heating |
| Heat sensitivity | Keep away from torch heat — heat can induce magnetism and split pieces |
| Care and cleaning | Warm soapy water and a soft brush; ultrasonic generally safe for solid pieces; avoid heat and strong acids |
| Birthstones | None |
| Availability | Plentiful — mass-produced beads, cabochons, carvings and intaglios at very low cost |
| Recognition | Grey-black metallic polish with a red-brown streak, distinctly heavy (SG ~5.2), hardness 5.5-6.5, weakly to non-magnetic (imitations are strongly magnetic) |
Varieties
Hematite
| Colour | dark grey to black with metallic polish |
| Transparency | opaque |
| Clarity type | Not applicable — opaque |
| Phenomena | None |
| Appearance | Mirror-polished steel-grey to black domes, beads and carvings, noticeably heavy and cool in the hand; intaglios and cameos take crisp relief; thin splinters and the streak show red-brown |
| Trade names | Kidney ore (botryoidal rough) • specularite (platy variety) |
| Misnomers | Alaskan black diamond • black diamond • black pearl (for beads — all misuses) |
| Typical sizes | Beads 3-15 mm; cabochons and intaglios from under a carat to very large carvings |
| Cutting styles | Beads • cabochons • intaglios and cameos • faceted small cuts (rare) • carvings |
| Key separations | vs imitation hematite ('hematine', a barium-strontium ferrite ceramic): hematine is strongly attracted to a magnet, often shows moulded detail and lower SG (~4.9-5.2 but variable); natural hematite is only weakly magnetic • vs cassiterite: cassiterite is brown and near-metallic with DR surface lustre, SG ~6.9 — much heavier • vs black onyx/glass: vitreous not metallic lustre, much lighter SG (~2.6) • vs hematine beads sold as 'magnetic hematite': magnetic therapy beads are ferrite ceramic, not hematite |
| Sources (localities) | England (Cumbria — historic botryoidal 'kidney ore' for jewellery) • Brazil (Minas Gerais — large modern producer) • China (major bead-carving supply) • Sweden (Kiruna) • Venezuela • Australia • USA |
| Availability | Plentiful; one of the cheapest opaque jewellery materials |
| Market notes | Mass-market beads and men's jewellery; 'magnetic hematite' clasp beads are ferrite imitations and should be labelled as such |
| Care notes | Durable in normal wear; re-polishing restores dulled metallic finish; keep from heat and acids; ultrasonic fine for solid pieces |
| In short | Hematite gives jewellery weight, mirror-grey polish and crisp intaglio carving at minimal cost. Teach the red streak and the magnet test — together they separate it from every common black lookalike, especially the ferrite imitations sold as 'magnetic hematite'. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–100.00 | $0.05 – $0.50 | commercial beads, cabs and intaglios | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Sources
GIA gem encyclopedia · mindat.org · Wikipedia
Data compiled and fact-checked against gemmological literature, October 2026 (JDMIS gem reference). Properties are ranges accepted in gemmological practice; individual stones vary.
See also
Gemstone reference entries: gem #193
Related materials: Corundum · Diamond · Opal · Quartz · Spinel · Topaz
Identification wizard · All 83 materials · Singapore gem labs