Is hessonite a garnet?
Hessonite is orange grossular garnet, the cinnamon stone: hardness 6.5 to 7, index 1.730 to 1.757 (IGS). How it parts from ruby, zircon and spessartine.
Yes. GIA and the International Gem Society both call hessonite a variety of grossular, the calcium aluminium garnet, in orange to brownish red; it has no IMA row. It reads once on a refractometer, 1.730 to 1.757 on the gem society’s figures. Ruby reads twice from 1.759, spessartine once at 1.800, and zircon, once also called hyacinth, from about 1.78 up.
In short
- The definition. GIA’s garnet quality factors say both tsavorite and hessonite are varieties of grossular, and that hessonite ranges from orange and orangy red to brownish red. The International Gem Society calls hessonite, also known as cinnamon stone, the yellow-orange to reddish orange variety of grossular garnet.
- Not a species name, but an old one. The September 2026 IMA-CNMNC Master List has a grossular row and none for hessonite or essonite; 0 lines contain hesson. Grew et al., American Mineralogist 98 (2013) decode hessonite, essonite and four cinnamon names as grossular, and record that grossular was described as Cinnamon Stone from Sri Lanka by Werner in 1803–1804, before the name grossular.
- The 1.76 ceiling. On the gem society’s figures hessonite gives one reading, 1.730 to 1.757. A stone that reads twice, or once above 1.76, is not hessonite: the corundum sheet’s ruby starts at 1.759 and reads twice, spessartine reads once at 1.800, low zircon starts near 1.78 on GIA’s figures, and titanite is over the refractometer’s limit.
- The jacinth split. The gem society says hessonites were among the gems called jacinth or hyacinth, terms that now mostly mean orange-red to red-brown zircon. Weighed, 20.00 g of hessonite reads 14.12 to 14.61 g in water and zircon 14.87 g or more on GIA’s range, 15.65 g or more on its sheet. Of 11 hyacinth and jacinth names in the IMA garnet report’s list, 5 decode to grossular.
- Where the ceiling fails, documented. Ruby’s lowest index on the corundum sheet is 0.002 above hessonite’s highest, so the count of readings decides, not the number. Titanite’s weight window, 14.25 to 14.44 g, lies inside hessonite’s. And the roiled, whisky-in-water look the gem society calls a help in identification is absent in some Afghan and Orissa, India hessonite.
| Stone, source | Optical class | Readings on a refractometer | Refractive index | Against the 1.76 ceiling | 20.00 g piece in water | Separated from hessonite by |
|---|---|---|---|---|---|---|
| Hessonite, IGS | Isotropic; may show anomalous birefringence | One | 1.730 to 1.757 | Under | 14.12 to 14.61 g; 14.52 g at the usual 3.65 | - |
| Grossular, Handbook sheet | Isotropic; weak strain birefringence | One | 1.734 | Under | 14.44 g | Nothing: the same species |
| Ruby, GIA | Doubly refractive; birefringence 0.008 to 0.010 | Two | 1.762 to 1.770 | Over, by 0.005 | 15.00 g (4.00) | Two readings; weight, 0.33 g or more |
| Corundum, Handbook sheet | Uniaxial (−) | Two | ω 1.767 to 1.772, ε 1.759 to 1.763 | Over, by 0.002 | 14.97 to 15.12 g | Two readings; weight |
| Spessartine, Handbook sheet | Isotropic; may show weak anisotropism | One | 1.800 | Over, by 0.043 | 15.23 g | Index; weight, 0.62 g |
| Zircon, GIA (low to high types) | Birefringence 0.000 to 0.059 | One to two | 1.810 to 1.984 (± up to 0.040) | Over, by 0.023 or more | 14.87 to 15.77 g | Index; weight, at least 0.26 g |
| Zircon, Handbook sheet | Uniaxial (+) | Over the limit | ω 1.925 to ε 2.015 | Over | 15.65 to 15.74 g | Index; weight, at least 1.04 g |
| Titanite, Handbook sheet | Biaxial (+) | Over the limit (IGS) | α 1.843 to γ 2.110 | Over, by 0.086 | 14.25 to 14.44 g | Index only: inside hessonite’s weight window |
Is hessonite a garnet? The definition in one sentence
Hessonite is orange to brownish red grossular: a garnet of the calcium aluminium species Ca3Al2(SiO4)3, sold under a variety name. GIA’s garnet quality factors say both tsavorite and hessonite are varieties of grossular, that hessonite ranges from orange and orangy red to brownish red, and that hessonite, like spessartine, often has eye-visible inclusions. The International Gem Society hessonite article calls it the yellow-orange to reddish orange variety of grossular garnet, also known as cinnamon stone, and writes its formula Ca3Al2Si3O12.
The IMA test, by script. The September 2026 IMA-CNMNC Master List lists grossular as Ca3Al2(SiO4)3, A, 1962 s.p., Russia, and has no row for hessonite or essonite; a case-insensitive whole-line scan finds 0 lines containing hesson. Grew et al., American Mineralogist 98 (2013), Appendix 2, decodes hessonite, essonite and essonit as grossular, and the four cinnamon names, cinnamon stone, cinnamon garnet, cinnamon granat and kanelstein, as grossular too.
What the species sheet adds. The Handbook grossular sheet gives cubic crystals, hardness 6.5 to 7, density 3.594, n = 1.734, and golden yellow, orange, brownish red and yellowish brown among its colours. It does not use the word hessonite. The gem society says hessonite can be softer than other garnets; the sheet’s figure is the one used here. The species page is grossular.
Hessonite or ruby? The 1.76 ceiling
The 1.76 ceiling: hessonite gives one refractometer reading, at or below 1.757, so a stone that reads twice or reads once above 1.76 is not hessonite. The International Gem Society gives hessonite n = 1.730 to 1.757; the grossular sheet prints 1.734. GIA’s ruby facts give 1.762 to 1.770 with birefringence 0.008 to 0.010, two readings 0.005 above the ceiling. The corundum sheet prints ω 1.767 to 1.772 and ε 1.759 to 1.763. Ruby is a variety of corundum on GIA’s page, and the reading rule is on corundum. One limit: the gem society says hessonite, like other grossulars, may show anomalous double refraction due to strain, so a strained stone is the case this rule handles least well; the weight then decides: ruby reads at least 14.94 g in water for 20.00 g on GIA’s range, hessonite at most 14.61 g.
Spessartine, the orange garnet. spessartine is the manganese garnet, and its sheet prints one index, 1.800, 0.043 above the ceiling, and density 4.190: 15.23 g in water for 20.00 g against hessonite’s 14.12 to 14.61 g. The gem society’s mandarin garnet is a spessartine. Both are garnets; only one is hessonite.
Heated rhodolite. The International Gem Society reports a 1997 experiment in which heating purplish rhodolite, an almandine–pyrope blend, gave a hessonite-type brownish colour at around 600 °C. Such a stone would still be a garnet but not grossular; pyrope and almandine read 1.714 and 1.830 on their sheets, either side of hessonite’s window, so a blend between them could read inside hessonite’s window and the ceiling alone would not catch it.
Hessonite or zircon? The jacinth split
The jacinth split: hessonite and zircon once shared the names jacinth and hyacinth, and a balance or a refractometer separates them. The International Gem Society says hessonites were, in past centuries, among the varied gems called jacinth or hyacinth, terms now little used that most commonly refer to orange-red to red-brown zircon. Worked as 20 − 20/D for 20.00 g, hessonite reads 14.12 to 14.61 g in water. GIA’s zircon facts give specific gravity 3.90 to 4.73, 14.87 to 15.77 g, so even the lightest zircon is 0.26 g heavier; the zircon sheet’s 4.6 to 4.7 reads 15.65 to 15.74 g, 1.04 g heavier.
The index agrees. GIA’s low-type zircon reads 1.810 to 1.815, ± 0.030, so no lower than 1.780: 0.023 above hessonite’s ceiling. Its high type reads 1.925 to 1.984 and the zircon sheet 1.925 to 2.015, over most refractometers’ limit. GIA gives low zircon a birefringence as small as 0.000, so a single reading does not by itself exclude zircon; the number does. The species page is zircon.
The hyacinth count. Grew et al.’s Appendix 2 lists 11 names containing hyacinth, hyazinth or jacinth: 5 decode to grossular, 5 to garnet without a species and 1, hyazinthe, to pyrope. Method: the appendix was parsed by word position into 817 name and species rows in run 24, and the names matched case-insensitively. The list covers garnet names only, so it cannot show the zircon sense of the words; the gem society’s statement does.
When the answer changes: titanite, the roiled look and treatments
Titanite weighs like hessonite, a documented failure of the balance. The titanite sheet’s density, 3.48 to 3.60, reads 14.25 to 14.44 g in water for 20.00 g, wholly inside hessonite’s 14.12 to 14.61 g. The International Gem Society records grossular garnets and zircons misidentified as titanite. The refractometer decides: hessonite reads on the scale and titanite, at 1.843 and up on its sheet, does not. The species page is titanite.
The roiled look is a help, not a test. The gem society says hessonite may show a roiled, heat-wave or whisky-in-water effect that can help confirm it, but that some relatively recent finds from Afghanistan and Orissa, India lack it. GIA calls it a turbulent inner appearance. Its absence does not rule out hessonite, and similar effects can occur in other gems, the gem society adds.
Treatments and imitations. The gem society reports occasional fracture fillings, including polymer, in low-grade hessonite, and warns of dyed glass, plastic and synthetic quartz imitations. A filled hessonite is still grossular; glass and quartz fail the reading. This page gives no other treatment claim. The general garnet checks are on how to tell if garnet is real, whose 1.71 line is not repeated here.
Why is it called hessonite? The name, cinnamon stone and localities
The name. The International Gem Society derives hessonite from the Greek hesson, inferior, and notes the archaic spelling essonite. Grew et al. attribute hessonite to Karl Cäsar Ritter von Leonhard and essonite to René Just Haüy in their Appendix 2, and record that grossular was described earlier as Cinnamon Stone (Kanelstein) from Sri Lanka by Werner in 1803–1804, and as Granat by Pallas in 1793; Werner’s grossular dates from 1808–1809.
Against the sheet. The gem society names Canada, Sri Lanka and Tanzania as major sources and says the fine cinnamon-coloured hessonites from Quebec have given cut gems up to about 25 carats, with brownish-orange stones from Asbestos, Quebec in the National Museums of Canada. The grossular sheet’s Distribution includes the Jeffrey mine, Asbestos, Quebec, and gems from the Merelani Hills, Tanzania; it does not say which variety each produced, and we add none. Sri Lanka is not on the grossular sheet.
The green grossular variety is on is tsavorite a garnet. Andradite, the other calcium garnet, is on is andradite a garnet, and a non-garnet often asked about on is vesuvianite a garnet. The classification questions are indexed at the collecting guides. This page gives no buying advice. Nothing on this site is offered for sale; the wanted list is the only commercial route.