Star Garnet Identification Guide
Identify star garnet by its dark red-brown almandine body, four- or six-rayed star, high density, hardness, and Idaho/India origin.
Read the full Star Garnet encyclopedia entry →
What Star Garnet Looks Like
Star garnet is an asteriated garnet, almost always iron-rich almandine (sometimes almandine-pyrope), that displays a star when cut en cabochon. The body color is deep red to reddish-brown, plum, or nearly black. The star comes from light reflecting off oriented rutile (or ilmenite) needle inclusions and is typically four-rayed, occasionally six-rayed — and star garnet is famous for sometimes showing a rare four-ray (and even six-ray) star, unusual among gems.
- Color: dark red, reddish-brown, purplish-red, near-black
- Luster: vitreous to slightly resinous; sub-adamantine
- Transparency: translucent to nearly opaque
- Habit: dodecahedral/trapezohedral crystals; star shown only in cabochons
Step-by-Step Field-ID Checklist
- Light the dome with a single source and rotate — a genuine star moves smoothly and stays centered.
- Count rays — four-rayed stars are characteristic of star garnet; six-rayed are rarer and prized.
- Confirm the deep red-to-brown body color typical of almandine.
- Heft the stone — garnet feels notably heavy for its size.
- Test hardness against glass (it scratches glass) and confirm no cleavage on any broken edge.
Key Diagnostic Tests
- Mohs hardness: 7–7.5 (almandine) — scratches glass.
- Streak: white.
- Cleavage: none; fracture conchoidal to uneven — absence of cleavage is diagnostic.
- Density: high, ~3.8–4.3 g/cm³ — heavier than most red look-alikes.
- Refractive index: ~1.79–1.81, high (strong luster).
- Magnetism: iron-rich almandine can show a weak-to-moderate pull on a strong neodymium magnet — a handy garnet confirmation.
- No acid reaction.
Common Look-Alikes and How to Tell Them Apart
- Star ruby (corundum): brighter red, six-rayed star, harder (9); star garnet is darker red-brown, often four-rayed, and softer.
- Non-star almandine cabochon: same mineral without oriented inclusions; no star forms.
- Red glass with a molded/printed star: the star is fixed and etched-looking; glass is softer (5–6), lighter, and may show bubbles. A real star glides with the light.
- Spinel / red tourmaline: rarely asteriated; spinel is singly refractive and octahedral, tourmaline is striated prismatic — habit and the star itself separate them.
- Rhodolite garnet: more purplish-red and usually transparent (faceted), seldom showing a star.
Where It Is Found
Star garnet is uncommon. The two premier sources are the Emerald Creek area near St. Maries, Idaho, USA (where it is the state gem and four- and six-ray stars occur) and India. It weathers out of mica schists and is recovered from stream gravels.
Frequently asked questions
How can you tell if it's real star garnet?
Real star garnet is a dark red-to-brown almandine cabochon, hardness 7–7.5 (scratches glass), with no cleavage and high density (~3.8–4.3). A genuine star (often four-rayed) glides across the dome under a single light, and iron-rich stones may respond weakly to a strong magnet.
Why do star garnets have four rays?
Most asteriated gems show six rays, but star garnet's inclusion geometry often produces a four-rayed star; six-rayed star garnets also occur and are especially valued.
Star garnet vs star ruby — how do I tell them apart?
Star ruby is brighter red, harder (9), and shows a six-rayed star; star garnet is darker red-brown, softer (7–7.5), denser-feeling, and commonly four-rayed.
Where is star garnet found?
Chiefly in Idaho (Emerald Creek near St. Maries, where it is the state gem) and in India; it is recovered from stream gravels eroded out of mica schist.
What does star garnet look like?
A deep red, reddish-brown, or plum cabochon that shows a floating four- or six-rayed silvery star when light moves across its polished dome.
Star Garnet identified by the community
Recent Star Garnet specimens identified with Rock Identifier.
