A Diamond is the only gem made of a single element, carbon.
Emerald is the green to greenish blue variety of beryl, a mineral species that also includes aquamarine as well as beryls in other colours.
The name “sapphire” belongs to the mineral species corundum that’s not red and doesn’t qualify as ruby.
Ruby is the most valuable variety of the corundum mineral species, which also includes sapphire.
Perhaps the best-loved gems of all time, pearls—both natural and modern cultured pearls—occur in a wide variety of colours.
Aquamarine is the green-blue to blue variety of the mineral beryl.
Quartz is one of the most common minerals on earth.
Garnets are a set of closely related minerals that form a group, resulting in gemstones in almost every colour.
Opal is known for its unique display of flashing rainbow colours called play-of-colour.
Tourmalines have one of the widest colour ranges of any gem species, occurring in various shades of virtually every hue.
Smoky quartz is a colour-variety of crystalline quartz.
Two different gem materials can correctly be called jade. Jadeite is one of them, and the other is nephrite. Both are actually metamorphic rocks made up of tiny interlocking mineral crystals.
Lemon quartz is created by heating amethyst, yellow quartz and iron together at extremely high temperatures.
Spinel, like garnet and diamond, is singly refractive, with the same physical properties in all crystal directions.
Tanzanite is the violet blue to blue violet variety of the mineral zoisite.
Topaz is allochromatic, which means that its colour is caused by impurity elements or defects in its crystal structure rather than by an element of its basic chemical composition.
Citrine - the transparent, pale yellow to brownish orange variety of quartz - is rare in nature. In the days before modern gemmology, its tawny colour caused it to be confused with topaz.
Peridot is the gem variety of the mineral olivine. Its chemical composition includes iron and magnesium, and iron is the cause of its attractive yellowish green colours.
Amethyst is the purple variety of the quartz mineral species.
Moonstone is a variety of the feldspar group mineral orthoclase.
