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Almandine Garnet
Almandine Garnet is nesosilicate (garnet group, pyralspite series), Fe3Al2(SiO4)3. In the hand, it rates 7 to 7.5 on the Mohs scale, and it runs deep red and brownish red. Rough crystals are usually well formed dodecahedra or trapezohedra with flat, glassy faces, and chips break with curved conchoidal surfaces rather than flat cleavage planes.
The geology.
Almandine Garnet carries the formula Fe3Al2(SiO4)3. It belongs to the cubic (isometric) system. Catalogues list it as nesosilicate (garnet group, pyralspite series).
It sits at 7 to 7.5 on the Mohs scale. The surface reads vitreous to resinous. Light behaviour is transparent to translucent. Specific gravity runs 3.95 to 4.30. The streak is white. It breaks with no cleavage; parting sometimes seen on {110}; subconchoidal to conchoidal fracture.
Almandine reads as a dark red with a brown or violet undertone rather than a pure red, and stones much over a centimeter across often look nearly black in the hand. Rough crystals are usually well formed dodecahedra or trapezohedra with flat, glassy faces, and chips break with curved conchoidal surfaces rather than flat cleavage planes. For its size it feels distinctly heavy, heavier than a red spinel or a piece of red glass of the same dimensions.
It reaches buyers as well formed dodecahedral crystals, trapezohedra, faceted gems or cabochons and tumbled stones.
The origins.
Almandine is the most common garnet, forming mainly in mica schists and gneisses produced by regional metamorphism of clay rich sediments, and also in contact hornfels, granites and eclogites. It survives weathering well and is widespread as a detrital mineral in sands and gravels. Documented localities include the Zillertal in Tirol, Austria; Falun, Sweden; the Barton mine at North Creek, Warren County, New York; Roxbury, Connecticut; Pernambuco and Bahia, Brazil; and Broken Hill, New South Wales, Australia.
On value, the database notes: almandine is abundant on every continent, so it is one of the least expensive garnets and the price per carat does not climb much with size. Value comes from bright, clean material that is not so dark it reads as black, and from the rare asteriated star garnets of Idaho and India.
Traditional associations.
Garnet is the birthstone for January and the stone traditionally given for a second wedding anniversary. The name comes from the medieval Latin granatus, meaning pomegranate, and red garnets were set in the jewelry of Egyptian pharaohs and carved into Roman signet rings used to stamp wax seals on documents. Sellers commonly connect almandine to the root chakra, to the zodiac signs Aquarius and Capricorn, and to the element of fire.
We keep this section because people ask. It sits below the geology on purpose, and none of it describes something the stone does.
Spotting the real thing.
Almandine reads as a dark red with a brown or violet undertone rather than a pure red, and stones much over a centimeter across often look nearly black in the hand. Rough crystals are usually well formed dodecahedra or trapezohedra with flat, glassy faces, and chips break with curved conchoidal surfaces rather than flat cleavage planes. For its size it feels distinctly heavy, heavier than a red spinel or a piece of red glass of the same dimensions.
Red glass is the oldest and still the most common imitation, and it gives itself away by being light in the hand, by rounded facet junctions and by gas bubbles inside. Garnet topped doublets, a thin slice of red garnet fused to colored glass, were made in quantity for antique and costume jewelry and can be spotted by looking for the join line at the girdle under a loupe. Almandine is also sold under misleading varietal names that borrow the prestige of other stones, so any description using the word ruby for a garnet should be checked against the actual species.
| Looks like | How to tell them apart |
|---|---|
| Ruby | Ruby is doubly refractive and strongly dichroic, so it shows two different reds as you rotate it and the back facet edges look doubled through a loupe. Almandine is singly refractive and does neither. |
| Red spinel | Spinel is noticeably lighter for its size (specific gravity near 3.6 against almandine's 4.0 or more) and tends to a purer, less brownish red. |
| Pyrope garnet | Pyrope is lighter in the hand and gives a brighter, more fiery red. A spectroscope shows almandine's three strong absorption bands, which pyrope either lacks or shows only weakly. |
At-home tests.
Before anyone talks you into a lab report, these are the checks worth doing yourself on almandine garnet.
| Test | What you should see |
|---|---|
| Under a loupe | Look down through the table with a loupe: almandine is singly refractive, so back facet edges appear as single crisp lines, never doubled as they do in ruby or tourmaline. |
| By weight | Heft it against a same size spinel, quartz or glass bead; almandine is one of the densest common red stones and feels obviously heavier. |
| By eye | Examine the girdle and any chips for flat, step like breaks, which would indicate a cleaving mineral rather than garnet. |
| By eye | Through a hand spectroscope, almandine shows a distinctive pattern of three strong absorption bands in the green and yellow green. |
If these checks leave you unsure, that is what appraisers are for. Do not file, heat or soak a piece to find out.
Care & handling.
At 7 to 7.5 on the Mohs scale it stands up to everyday wear. It will still chip on a hard knock, so treat edges and points with respect.
It breaks with no cleavage; parting sometimes seen on {110}; subconchoidal to conchoidal fracture, which is worth knowing before you set it or drop it.
Most damage happens during cleaning, not wearing. Avoid steamers, ultrasonic tanks and anything from under the sink.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is Fe3Al2(SiO4)3. Crystal system: Cubic (isometric). Specific gravity: 3.95 to 4.30. Streak: White. Cleavage and fracture: No cleavage; parting sometimes seen on {110}; subconchoidal to conchoidal fracture.
How it reaches the market
Almandine is the most common garnet, forming mainly in mica schists and gneisses produced by regional metamorphism of clay rich sediments, and also in contact hornfels, granites and eclogites. It survives weathering well and is widespread as a detrital mineral in sands and gravels. Documented localities include the Zillertal in Tirol, Austria; Falun, Sweden; the Barton mine at North Creek, Warren County, New York; Roxbury, Connecticut; Pernambuco and Bahia, Brazil; and Broken Hill, New South Wales, Australia.
What it gets confused with
Ruby: Ruby is doubly refractive and strongly dichroic, so it shows two different reds as you rotate it and the back facet edges look doubled through a loupe. Almandine is singly refractive and does neither.. Red spinel: Spinel is noticeably lighter for its size (specific gravity near 3.6 against almandine's 4.0 or more) and tends to a purer, less brownish red.. Pyrope garnet: Pyrope is lighter in the hand and gives a brighter, more fiery red. A spectroscope shows almandine's three strong absorption bands, which pyrope either lacks or shows only weakly..
What it is worth
Almandine is abundant on every continent, so it is one of the least expensive garnets and the price per carat does not climb much with size. Value comes from bright, clean material that is not so dark it reads as black, and from the rare asteriated star garnets of Idaho and India.
Where buyers get caught
Red glass is the oldest and still the most common imitation, and it gives itself away by being light in the hand, by rounded facet junctions and by gas bubbles inside. Garnet topped doublets, a thin slice of red garnet fused to colored glass, were made in quantity for antique and costume jewelry and can be spotted by looking for the join line at the girdle under a loupe. Almandine is also sold under misleading varietal names that borrow the prestige of other stones, so any description using the word ruby for a garnet should be checked against the actual species.
One more thing
Almandine is the backbone of the industrial abrasives trade. Henry Hudson Barton began mining it at Gore Mountain in New York in 1878 because he judged garnet would make better sandpaper than anything then on the market, and garnet from those deposits is still crushed for waterjet cutting and abrasive blasting.
An education-first guide.
There is nothing to buy on this page. Almandine Garnet is not part of our catalogue, and the guide is here anyway because somebody searching the name deserves a straight answer.
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