Diamond β The Hardest Gem, Made of Pure Carbon
Diamond forms when carbon atoms bond tightly in an octahedral structure, crystallizing deep in the mantle under intense heat and pressure before volcanic activity carries it near the surface. Pure diamond is colorless, but trace nitrogen can tint it yellow, and trace boron can tint it blue. India was historically a major source, followed by South Africa and other regions.
Ruby β Corundum Colored Red by Chromium
Ruby is a variety of corundum (aluminum oxide) that owes its red color to trace chromium. Myanmar's Mogok region has long been prized for high-quality rubies, with Thailand, Sri Lanka, and Mozambique also significant sources. Notably, any corundum that isn't red is classified as sapphire instead.
Sapphire β Every Color of Corundum Except Red
Sapphire is the same corundum mineral as ruby, but iron and titanium give it its characteristic blue color. Any red corundum is called ruby; every other color β yellow, pink, green, and more β is called "fancy sapphire." Kashmir, Sri Lanka, Madagascar, and Australia are notable sources.
Emerald β Beryl Colored Green by Chromium and Vanadium
Emerald is beryl with trace chromium or vanadium giving it its deep green color. Colombia's Muzo mine has historically been a top source, with Zambia and Brazil also major producers. Ancient Egypt is said to have mined emeralds, and Cleopatra was famously fond of them.
Pearl β An Organic Gem Grown Inside a Shell
Unlike other gems, pearl isn't a mineral β it forms when a mollusk like an oyster or mussel deposits layer upon layer of nacre (calcium carbonate) around a foreign particle. Natural pearls are extremely rare, so most pearls sold today are cultured, grown by intentionally inserting an irritant. Kokichi Mikimoto of Japan is widely credited with commercializing pearl cultivation in the early 20th century.
Opal β A Gem That Diffracts Light Into a Rainbow
Opal is a hydrated silica gem whose tiny, orderly arrangement of silica spheres diffracts light, producing a shifting rainbow "play of color" depending on the viewing angle. Australia has long produced the majority of the world's opal, and black opal β with vivid color against a dark background β is especially prized.
Amethyst β Purple Quartz Colored by Iron
Amethyst is quartz that turns purple from trace iron combined with natural background radiation. Brazil, Uruguay, and Zambia are major sources. Since purple was historically a rare and prized color, amethyst was long associated with royalty and clergy, and today it's commonly listed as the birthstone for February.
Turquoise β A Sky-Blue Gem Formed by Copper and Aluminum
Turquoise is a phosphate mineral containing copper and aluminum, known for its opaque sky-blue to blue-green color. Despite the name, Turkey isn't actually a major source β the name comes from the trade route through Turkey by which it first reached Europe. It has long been prized in ancient Persian and Egyptian jewelry, as well as by Native American cultures such as the Navajo and Zuni.
Garnet β A Silicate Gem Family With Many Colors
Garnet isn't a single mineral, but a group name for several closely related silicate minerals. Its name is said to come from its resemblance to pomegranate seeds. While deep red is the most familiar color, garnet also occurs in green, orange, and other colors, and it is widely listed as the birthstone for January.
Topaz β A Silicate Gem Ranging From Colorless to Golden
Topaz is a silicate mineral containing aluminum and fluorine, typically colorless or pale in its natural state. The vivid blue topaz commonly sold today is usually colorless topaz that has been heat-treated, while deep-orange "imperial topaz" is prized in its natural state. It's also commonly listed among the birthstones for November.