The Beryl family
Beryl stones are made of specific amounts of aluminum, beryllium, silica and oxygen arranged to create a hexagonal crystal. In their basic state, beryls are colorless, though their chemical structure enables them to hold a wide range of impurities, creating a wealth of hues and subsets. The most iconic variety, emerald, gets its deep green hues from chromium and vanadium. Its fellow beryl birthstone, aquamarine, achieves its oceanic shades with the help of iron.
Between their rainbow of colors and their Mohs hardness of 7.5-8, many beryls are suited for cuts that concentrate their hues, making them richer. At the same time, their long natural crystals make them ideal for geometric shapes with parallel facets, also known as step cuts. Emeralds in particular have been shaped into rectangular step cuts so often they’re also known as emerald cuts.
The Quartz family
Quartz is a mineral of contradictions. The stone is a common component of soil, yet takes a place of honor in crown jewels. Its silica dioxide crystals take on long triangular shapes that bond together, forming tall hexagons that may be microscopic, or large enough to be held in both hands.
Of the jewelry grade varieties of quartzes, amethyst and citrine are the most prized, though other types such as rose quartz are also used. Not only are these stones have the same base structure, but they all get their distinctive hues through variations on iron impurities. Iron blends with titanium or manganese to make rose, ferric compounds create tawny citrine, and iron combined with radiation tints amethyst. Very rarely, two types of ferric impurities will affect the same rough, creating a bicolor yellow and purple quartz known as ametrine.
The Garnet family
Garnets are a diverse family of stones with a common core. Their chemical composition consists of twelve units of oxygen, three of silica, three of one variable element, and two of another. This formula creates crystals with a Mohs hardness between 7-7.5 which takes on the shape of dice with twelve of twenty four sides.
Differing ingredients in the chemical formula make the garnet’s wide range of colors. For example, pyrope gets its iconic red from magnesium and aluminum, while uvavorite’s bright green comes from calcium and chromium. Varying elements also affect the luster, creating a waxy sheen on one stone, or a resinous gleam on another. With so many types, there is a garnet for every taste.
The Chalcedony family
Though quartz and moganite are both silica dioxide, the molecular shape of the former takes on triangular and hexagonal shapes while the latter is rectangular. When they are intermingled on a sub microscopic level, chalcedony is born. This mineral family contains many types of prized stones which are often multicolored, displaying streaks, spots or mottled patterns. Examples include jasper, onyx, heliotrope and carnelian.
Between the stone’s colorful nature and moderate Mohs hardness of 6.5 to 7, chalcedony has been favored for millennia for jewelry and art. Along with beads and signet rings, it makes ideal material for cameos. Depending on the type, as one layer is carved away, lower layers reveal contrasting shades, enhancing the image. From museum quality pieces to causal bead jewelry, chalcedony is whatever you want it to be.
The Corundum family
Corundum is a mineral family made of two parts aluminum and three parts oxygen. Its crystal takes on a triangular shape, fastened together with other triangles to form hexagons. Though the stone is most famous for red rubies and blue sapphires, it’s naturally colorless and available in a rainbow of hues.
The stone has a Mohs hardness of 9, second only to diamonds. This makes corundum ideal for rings, bracelets, and other pieces of jewelry prone to bumps and frequent wear. It’s also strong enough for cleaning treatments, such as high pressure steam, that many other gemstones are too fragile to withstand.