Natural Ruby Gemstones

Natural Ruby Gemstones

Ruby is the red variety of corundum (Al2O3), colored by trace chromium. With a Mohs hardness of 9 it is one of the hardest natural gemstones after diamond, and alongside diamond, sapphire and emerald it is one of the classic "big four" gemstones. The same chromium that gives ruby its color also makes many rubies glow red under ultraviolet light, which adds to their brightness even in ordinary daylight.

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Gemstone guide

Natural Ruby Gemstones

About ruby

Ruby and sapphire are the same mineral: corundum is called ruby only when it is red, and every other color is sapphire. Ruby is the traditional birthstone for July and has been one of the most valued gemstones for centuries. Most ruby today comes from East Africa and Southeast Asia, including Mozambique, Madagascar, Tanzania, Thailand and Myanmar. Heating is the most common treatment: careful heating improves color and clarity, and the result is permanent.

What you'll find in this collection

Most of our rubies come from Madagascar, with smaller numbers from Thailand, Tanzania, Mozambique and other African sources. You'll find faceted ovals, rounds, pears and cushions as well as smooth cabochons, in shades from pinkish red to deep red, from under a quarter of a carat to larger cabochons. Most stones are heated; unheated stones are labeled Untreated and also have their own Untreated Rubies collection. Every ruby is sold loose, with its carat weight and millimetre size given so you can match it to a setting.

How to recognise ruby

Ruby is doubly refractive and strongly dichroic: viewed from different directions, one stone can show a purplish red and an orange red. Under magnification natural rubies often show fine needles of rutile, called silk, along with small crystals and fingerprint-like feathers; when the silk is dense and well aligned, a cabochon can show a six-rayed star. Red spinel and red garnet can look similar, but both are singly refractive and show no dichroism.

Caring for ruby

Ruby is hard and tough and has no cleavage, so it suits everyday rings. Clean it with warm soapy water and a soft brush, then rinse and dry. Avoid ultrasonic and steam cleaners for any stone with open fractures, and keep ruby jewelry away from harsh household chemicals.

Every ruby is natural, and each listing gives its weight, size, origin and treatment, with photos of the actual stone.