Key properties
| Chemical formula | Ca5(PO4)3(OH) (hydroxyapatite, about 65%) with collagen and elastin (about 35%); ivory is dentine |
| Crystal system | None (biological composite, amorphous) |
| Mohs hardness | 2.3-2.8 |
| Toughness | Fair |
| Refractive index | 1.535-1.540 |
| Optic character | Aggregate (AGG) |
| Specific gravity | 1.70-2.00 |
| Cleavage | None |
| Fracture | Splintery to uneven |
| Habit | Not applicable; solid dentine from tusks and large teeth, worked as blocks, rounds and sheets |
| Lustre | Dull to greasy; polish: Greasy, with a distinctive soft 'ivory' glow |
| UV fluorescence | Weak to strong bluish white to violet-blue under LW and SW, usually stronger in LW; gradually fades as ivory ages |
| Pleochroism | None |
| Cause of colour | Natural white to cream; yellows with age, light and skin oils; darker brown-black from staining, smoking or burial. Dyed and 'antiqued' colours are applied |
| Typical inclusions | Diagnostic Schreger lines: intersecting curved cross-hatch ('engine-turned') pattern seen on cross-sections; elephant ivory Schreger angles exceed about 100 degrees, mammoth angles are below about 90 degrees. No canal holes (that is bone) |
| Stability | Fair. Yellows with age and light; shrinks, checks and cracks with heat or dryness; attacked by acids (nitric and phosphoric soften it); absorbs water and stains |
| Heat sensitivity | High; shrinks and discoulours under heat, scorches and burns (protein odour) |
| Care and cleaning | Wipe with a dry soft cloth; if needed a barely damp cloth, then dry immediately. Never ultrasonic, steam, soak or bleach. Store at stable humidity away from light and heat |
| Birthstones | None |
| Availability | Legal commercial trade effectively ended: African elephant Appendix I (1989 international ban), with near-total US (2016) and China (2017) domestic bans. Only documented pre-ban antiques, some mammoth fossil ivory and a few other regulated categories circulate |
| Recognition | The historic 'white gold' of carving: netsuke, okimono, scrimshaw, piano keys, billiard balls, bangles and beads. Every buyer must now be able to prove legality |
Varieties
Ivory
| Colour | opaque white to cream and light yellow, ageing toward deeper yellow-brown |
| Transparency | translucent edges to opaque |
| Clarity type | Opaque with visible Schreger structure on cross-sections |
| Phenomena | None |
| Appearance | Even, warm white with a greasy soft lustre; cross-sections show the engine-turned Schreger cross-hatch, longitudinal cuts show linear grain |
| Trade names | green ivory (historical finest African, Tanzania) • Cape ivory (South Africa) • hard ivory (Ambriz, Angola) • mammoth ivory (fossil, legal in most markets) • walrus, hippo, narwhal, sperm-whale ivory by source animal |
| Misnomers | 'French ivory' (celluloid or casein plastic, not ivory) • 'vegetable ivory' (tagua nut) • 'ivory' applied to white bone, shell, plastic and even white jade • odontolite sold as turquoise |
| Typical sizes | Elephant tusks average 9-27 kg (Asian smaller), giving large carving blocks; beads 4-20 mm; bangles standard; mammoth bark ivory in curved slabs |
| Cutting styles | Carvings (netsuke, okimono, figures), cabochons, bangles, beads, piano keys, veneers and inlay, scrimshaw engraving |
| Key separations | vs bone: bone shows round dark canal dots, ivory shows Schreger cross-hatching; bone often cheaper-looking and pitted. vs vegetable ivory: tagua is granular, no Schreger, SG about 1.40 vs ivory about 1.85. vs plastic: plastic SG about 1.3, hot point melts, no structure; 'French ivory' shows mould lines. vs horn/tortoiseshell: protein materials burn with hair odour and lack Schreger lines; SG lower. Mammoth vs elephant: Schreger angle (mammoth under about 90 degrees, elephant over about 100); mammoth often takes bark-like outer curvature and blue-green mineral staining |
| Sources (localities) | Historical elephant ivory from East and West Africa (Kenya, Tanzania, Senegal) and Asia (India, Sri Lanka, Myanmar, Thailand) • mammoth from Siberian and Alaskan permafrost (legal fossil material) • walrus from Arctic peoples' regulated subsistence carve • hippopotamus and warthog from Africa • all elephant products now trade-restricted |
| Availability | Effectively unavailable as new material; documented antiques, estate pieces and legal mammoth ivory only |
| Market notes | Legal risk is the dominant issue: CITES Appendix I for elephants, near-total domestic bans in China and the US. Any ivory offered must come with provenance; misdeclarations carry penalties. Mammoth ivory is the usual legal white carving material |
| Care notes | Avoid heat, direct light, dryness (cracks) and all acids and solvents; wipe with dry cloth; stable humidity storage; never immerse strung beads |
| In short | True ivory - dentine from elephant and allied species - is a soft, warm white carving material identified by Schreger cross-hatching, now restricted to documented antiques and legal fossil mammoth. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 0.50–5.00 | $5.00 – $50.00 | legal pre-ban estate beads and bangles | 2026-10-26 |
| 5.00–50.00 | $20.00 – $200.00 | fine antique carved ivory / legal mammoth | 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
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 #140 · gem #185
Related materials: Corundum · Diamond · Opal · Quartz · Spinel · Topaz
Identification wizard · All 83 materials · Singapore gem labs