Merelani Mint Garnet Identification Guide
Identify Merelani mint garnet, a pale mint-green grossular from Tanzania, and separate it from tsavorite, peridot, green tourmaline, and chrome diopside.
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What Merelani Mint Garnet Looks Like
Merelani mint garnet is a light, minty green variety of grossular garnet (calcium-aluminum garnet, Ca3Al2Si3O12) from the Merelani Hills of Tanzania. It is essentially a pale, pastel cousin of tsavorite, colored by trace vanadium and/or chromium. The hallmark is a soft, slightly yellowish to bluish mint green with high transparency and lively brilliance.
- Color: pale to medium mint green, sometimes with a faint yellow or blue cast
- Luster: vitreous, bright
- Transparency: transparent, often very clean (eye-clean stones common)
- Habit: as garnet, it forms equant dodecahedral/trapezohedral crystals; faceted gems are most common in the trade
Step-by-Step Field-ID Checklist
- Note the pastel mint color — lighter and softer than the vivid grass-green of tsavorite.
- Check transparency and brightness: high clarity and strong luster point to a garnet rather than a translucent stone.
- Look for crystal form: rounded, equant dodecahedral garnet crystals (no prismatic shape).
- Confirm singly refractive behavior: garnet shows no doubling of back facets (peridot does double).
- Check for no cleavage: garnet breaks conchoidally, not along flat planes.
Key Diagnostic Tests
- Hardness: 6.5-7.5 (grossular), scratches glass.
- Refractive index: ~1.73-1.75, singly refractive (isotropic) — a key separator from doubly refractive look-alikes.
- Density: ~3.5-3.7, high; feels heavy for its size.
- Streak: white.
- Cleavage: none; conchoidal fracture.
- Spectroscope/filter: vanadium/chromium coloring may show absorption features; some stones react under a Chelsea filter.
Common Look-Alikes and How to Tell Them Apart
- Tsavorite: the same grossular species but a deeper, more saturated green. Mint garnet is simply the lighter pastel grade — color is the distinction, not species.
- Peridot: olive-green and strongly doubly refractive (you can see doubled back facets through the table). Garnet is singly refractive — a definitive separator.
- Green tourmaline: prismatic crystals, doubly refractive, often with strong pleochroism; garnet is isotropic and equant.
- Chrome diopside: softer (5.5-6.5), darker green, doubly refractive with cleavage; garnet is harder with no cleavage.
- Green glass/CZ: glass is singly refractive but softer and warmer to the touch; check hardness and inclusions.
Where It Is Typically Found
The primary source is the Merelani Hills, Lelatema Mountains, Arusha Region, northern Tanzania — the same graphite-bearing metamorphic deposits that produce tsavorite and tanzanite. Mint grossular occurs in graphitic gneisses and calc-silicate rocks within this East African metamorphic belt.
Frequently asked questions
What is the difference between Merelani mint garnet and tsavorite?
Both are vanadium/chromium-colored grossular garnet from the Merelani area. Tsavorite is a vivid, saturated green, while Merelani mint garnet is the lighter, pastel mint-green grade. They are the same species separated only by color intensity.
How can you tell Merelani mint garnet from peridot?
Garnet is singly refractive, so its back facets never appear doubled, while peridot is strongly doubly refractive and shows obvious facet doubling. Peridot is also more olive-toned, whereas mint garnet is a cooler mint green.
Is Merelani mint garnet a real garnet?
Yes. It is genuine grossular garnet colored by trace vanadium and chromium, with a hardness of about 6.5-7.5, refractive index near 1.73, and high specific gravity around 3.6.
Where does Merelani mint garnet come from?
It comes from the Merelani Hills in the Arusha Region of northern Tanzania, the same metamorphic deposits that produce tsavorite and tanzanite.