Peridot Identification Guide
A practical field guide to recognizing gem peridot by its olive-green color, doubling, and link to basalt and meteorites.
Read the full Peridot encyclopedia entry →
What Peridot Looks Like
Peridot is gem-quality forsteritic olivine, a magnesium-iron silicate. Its defining feature is a warm, oily, yellowish-green to olive-green color caused by iron, with almost no blue or gray cast. Pure bottle-green and brownish-green stones also occur. Peridot has a vitreous (glassy) to slightly greasy luster, is transparent to translucent, and forms stubby prismatic crystals, but in the field it most often turns up as rounded grains, sugary masses, or olive-green specks in dark volcanic rock.
Step-by-Step Field ID Checklist
- Check the color. Look for a consistent yellow-green to olive tone. Peridot is idiochromatic — the color comes from the mineral itself, so it does not shift dramatically with lighting.
- Look at the host rock. Green grains studding black basalt, or olive nodules (dunite xenoliths) in lava, strongly suggest olivine/peridot.
- Test hardness. Peridot is Mohs 6.5–7; it scratches glass and a steel knife will not scratch it.
- Hunt for doubling. Through a loupe, peridot's high birefringence makes back facet edges appear doubled — a near-diagnostic clue.
- Feel the heft and luster. It has a slightly oily sheen and conchoidal fracture on broken faces.
Key Diagnostic Tests
- Hardness: 6.5–7. Scratches glass cleanly.
- Streak: White to colorless.
- Cleavage/fracture: Poor cleavage; conchoidal, brittle fracture.
- Birefringence: Strong (~0.036) — visible facet doubling under magnification, the single best test.
- Density: 3.27–3.48, noticeably heavy for its size.
- No magnetism, no acid reaction.
Common Look-Alikes and How to Tell Them Apart
- Green tourmaline (verdelite): Often darker, more blue-green; weaker doubling and stronger pleochroism. Tourmaline crystals are striated triangular prisms.
- Chrome diopside: Deeper, richer emerald-green; softer (5.5–6.5) and color comes from chromium rather than iron.
- Green glass / moldavite: Glass is singly refractive (no doubling) and may contain bubbles. Always check for facet doubling.
- Emerald: Bluer green, much rarer in matrix, and shows no doubling; emerald is beryl.
- Demantoid garnet: Singly refractive, higher dispersion (fire), and harder edges.
The doubling-plus-hardness combination separates peridot from nearly every green look-alike.
Where Peridot Is Found
Peridot forms deep in the mantle and arrives at the surface in basalt and as olivine xenoliths. Classic localities include Peridot Mesa on the San Carlos Apache Reservation (Arizona), Zabargad Island in the Red Sea (Egypt), Pakistan's Kohistan region, Myanmar, and China. Beach sands rich in olivine (Hawaii's green-sand beaches) and even stony-iron pallasite meteorites carry gem olivine.
Frequently asked questions
How can you tell if it's real peridot?
Look for a consistent yellow-green to olive color, a hardness of 6.5–7 that scratches glass, and especially facet doubling under a loupe. Glass imitations are singly refractive and often contain bubbles.
What does peridot look like in the rough?
Rough peridot appears as olive-green to yellow-green glassy grains, rounded pebbles, or sugary masses, frequently embedded in black basalt or in olive-colored dunite nodules from lava flows.
Peridot vs emerald — how do I tell them apart?
Emerald is a bluer, richer green with no facet doubling, while peridot is yellow-green and shows strong doubling under magnification. Peridot is also far more common in volcanic settings.
Is peridot the same as olivine?
Yes — peridot is simply the gem-quality, transparent variety of the mineral olivine (forsterite). Most olivine is too small or included to cut, but clean material is sold as peridot.
Where can I find peridot in the field?
Search young basalt flows and cinder cones for green grains, olivine xenoliths, and weathered nodules; famous spots include San Carlos in Arizona and Hawaii's green-sand beaches.
Peridot identified by the community
Recent Peridot specimens identified with Rock Identifier.
