Key properties
| Chemical formula | Ca3Al2(SiO4)3 |
| Crystal system | Cubic |
| Mohs hardness | 6.5-7.5 |
| Toughness | Fair to good |
| Refractive index | 1.730-1.760 |
| Optic character | SR (singly refractive; isotropic) - anomalous double refraction sometimes visible |
| Dispersion | 0.0280 |
| Specific gravity | 3.57-3.73 |
| Cleavage | None; parting sometimes distinct |
| Fracture | Conchoidal to uneven |
| Habit | Dodecahedral crystals in skarns and marbles; gem rough often as pebbles or grains |
| Lustre | Vitreous, sometimes greasy; polish: Vitreous |
| UV fluorescence | Inert to weak orange in long-wave UV for some pale and near-colourless material |
| Pleochroism | None (isotropic) |
| Cause of colour | Variable trace chemistry: Fe3+ yellows hessonite; V/Cr greens tsavorite; Mn pinks rosolite; pure material is colourless (leuco-garnet) |
| Typical inclusions | Hessonite: stubby rounded included crystals (apatite etc.) producing a granular 'heat-wave' or 'whisky' effect • tsavorite: graphite, diopside, fluid films • mali-type: fine veil patterns |
| Stability | Stable to light and chemicals; slightly attacked by hydrofluoric acid |
| Heat sensitivity | Abrupt temperature change can fracture; liquid-included stones risky in ultrasonic |
| Care and cleaning | Ultrasonic usually safe, risky if liquid-included • steamer never • warm soapy water safe |
| Birthstones | January (garnet) • Aquarius |
| Availability | Plentiful for hessonite and yellow grossular; green tsavorite is separate and limited |
| Recognition | Hessonite has modest recognition as 'cinnamon stone'; colourless grossular is a collector curiosity |
Varieties (2)
Hessonite
| Colour | orangy yellow to reddish orange and brownish orange - 'cinnamon' tones |
| Transparency | transparent |
| Clarity type | Type II - typically included; the granular 'heat-wave' look is characteristic |
| Phenomena | None |
| Appearance | A warm cinnamon-to-honey orange, usually slightly sleepy because of its granular internal texture - hessonite rarely looks glassy like spessartite. |
| Trade names | essonite (older spelling) • cinnamon stone |
| Misnomers | hyacinth / jacinth (old ambiguous terms also used for zircon) • 'cinnamon stone' sometimes treated as a misnomer |
| Typical sizes | Widely available from melee to 10 ct+; clean large stones common relative to other garnets |
| Cutting styles | Faceted in all shapes; beads and cabochons in ornamental use |
| Key separations | vs spessartite: spessartite brighter orange, manganese bands 410-430 nm, SG 4.15, no granular look • vs topazolite: topazolite RI 1.888 and much higher fire • vs citrine: citrine DR, RI 1.544-1.553 • vs fire opal: opal SG ~2.0, softer, may fluoresce • vs glass: bubbles, wrong SG, no 407/430 nm bands |
| Sources (localities) | Sri Lanka (major) • India (major) • Brazil • Canada (Jeffrey mine, Asbestos, Quebec) • Tanzania • Madagascar • Mexico • Italy |
| Availability | Plentiful and affordable; fine clear orange always in demand for period-style jewellery |
| Market notes | A staple of Victorian and estate jewellery. Canadian Jeffrey mine material (closed 2002) is prized by collectors. Hessonite spectrum may show bands at 407 and 430 nm. |
| Care notes | Standard garnet care; avoid steamers and thermal shock |
| In short | Hessonite is the cinnamon-orange grossular garnet, instantly recognised under the loupe by its granular, heat-wave internal texture. Abundant and affordable, it is the classic orange garnet of antique jewellery. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–5.00 | $15.00 – $100.00 | commercial to fine | 2026-10-26 |
| 5.00–15.00 | $30.00 – $150.00 | fine large | 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.
Colourless Grossular
| Colour | colourless to very pale yellow or green tint |
| Transparency | transparent |
| Clarity type | Type II - typically included |
| Phenomena | None |
| Appearance | A bright, neutral white gem with garnet fire (dispersion 0.028) - lively despite modest brilliance, and completely natural. |
| Trade names | leuco-garnet (colourless grossular) |
| Misnomers | occasionally passed off as diamond substitute in tourist markets |
| Typical sizes | Usually small (under 3 ct); faceted clean stones are rare enough to be collector items |
| Cutting styles | Faceted, brilliant styles to exploit dispersion |
| Key separations | vs colourless zircon/CZ/YAG/glass: check RI (grossular 1.74 SR), SG 3.61; man-mades show bubbles/swirls • vs colourless sapphire: sapphire DR 0.008, RI 1.762-1.777 • vs diamond: diamond RI 2.417, adamantine lustre, sharp facet edges |
| Sources (localities) | Canada (Jeffrey mine) • Tanzania • Madagascar • Mali region material ranges near colourless |
| Availability | Rare - a collector stone rather than a jewellery staple |
| Market notes | Genuinely colourless grossular is scarce; most 'white garnet' on the market is very pale yellow-green. Sold mostly by specialist dealers. |
| Care notes | Standard garnet care |
| In short | Colourless grossular (leuco-garnet) is a rare, natural white garnet with notable fire, cut mostly for collectors from Canadian and East African rough. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 0.50–3.00 | $20.00 – $120.00 | collector market | 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 #108 · gem #162
Related materials: Almandine Garnet · Andradite Garnet · Hydrogrossular Garnet · Pyrope Garnet · Rhodolite Garnet · Spessartine Garnet · Tsavorite Garnet
Identification wizard · All 83 materials · Singapore gem labs