Peridot

What causes the color: The olive-green color comes from iron (Fe2+) that's built directly into olivine's chemical formula, not present as a trace impurity the way color-causing elements are in most other gems — which is why peridot has no colorless, red, or blue natural variety the way quartz or beryl do.

How it forms: Forms deep within Earth's upper mantle and reaches the surface carried by basaltic volcanic eruptions, often visible as small green crystals embedded directly in volcanic rock. Separately, and unusually for a gem material, peridot-quality olivine also occurs in pallasite meteorites, a rare stony-iron meteorite type, making it one of the few gemstones with a genuine, documented extraterrestrial source.

Treatments & imitations: Essentially never treated — peridot's color is stable and doesn't respond well to the heat treatments common in many other colored gems, so what you see in a natural stone is generally its untreated, natural color.

Real vs. fake: Genuine peridot shows strong double refraction — held under a loupe, the back facet edges appear visibly doubled, an unusually pronounced version of an effect that's subtle or invisible in most other gems. It's also consistently olive-to-yellowish green (never the pure bluish-green of emerald or tourmaline) and noticeably less dense than similarly-colored glass imitations.

Historical use: Ancient Egyptians mined peridot on Zabargad Island in the Red Sea for more than 3,500 years, calling it the 'gem of the sun,' and gemological historians believe many stones ancient Egyptian and Roman writers described as emerald — including some pieces attributed to Cleopatra's jewelry — were very likely peridot instead, given how similar the two can look and how much rarer fine emerald genuinely is. In Hawaiian tradition, small olivine sand grains found on some beaches (sometimes called 'Hawaiian diamond') are associated with Pele, the volcano deity.

Metaphysical tradition: Abundance, positivity, and protection from negativity are the qualities modern crystal-healing tradition assigns to peridot at the heart and solar plexus chakras, drawing loosely on its ancient nickname as the 'gem of the sun.'

How to use it: Rings and pendants are common choices for it, prized for how well its bright, warm green tone catches light.

Cleansing & care: Durable (Mohs 6.5-7) but sensitive to sudden temperature changes and some household acids, which can etch its surface over time — warm soapy water is safe, but ultrasonic cleaners and harsh chemical cleaners are best avoided.