We tend to lump rocks, minerals, and gemstones together into the somewhat amorphous category of lump-shaped things that come from the ground. But, in fact, they are – figuratively speaking – three very different kettles of fish. So what exactly is the distinction between them? Read on to find out.
Rock, Paper, Mineral?
While a mineral is (according to the Oxford English Dictionary) a solid, naturally-occurring inorganic substance, a rock is an aggregate of minerals. A rock can be made of one mineral, or several. And, since there are over four thousand minerals on Earth, the combinations are endless. Granite, for instance, is composed of quartz, biotite, and feldspar. Those of you who took matric geography will remember that there are three kinds of rock: sedimentary, igneous, and metamorphic. Igneous rock forms from the cooling and hardening of lava, and can be either plutonic (when lava cools slowly within the Earth’s crust) or volcanic (when it erupts from the surface as lava or fragmental ejecta). Metamorphic rock is formed when either sedimentary or igneous rock is subjected to a temperature or pressure that is different from the conditions under which it was initially formed, causing the physical and chemical properties of the rock to change. Lastly, sedimentary rock manifests after the steady accumulation (and cementation) of minerals, fragments of other rocks, and organisms – a much less dramatic process.
Gemstones: Precious and Semiprecious
Gemstones are a particular type of mineral called a crystal, which is formed when – and only when – a very particular set of conditions occurs under the Earth’s surface. They are generally classed as either precious, or semiprecious. The precious gemstones are the diamond, sapphire, ruby, and emerald. Diamonds are formed under extremely high pressure, hundreds of kilometres below the Earth’s surface, while rubies and sapphires are formed out of corundum. Emeralds are formed from a mineral called beryl. The semiprecious stones are called so because they are more widely available. Amethyst, for instance, was termed “precious” until a large reserve of it was discovered in Brazil. There are many different kinds of semiprecious stones, ranging from the blue-tinged topaz, turquoise, and aquamarine, to the greenish peridot, jade, and malachite. Citrine, tourmaline, and garnet are warmer in colour, while the opal, moonstone, and pearl are distinctly milky in hue. Before these stones – both precious and semiprecious – are cut and polished, they could pass for ordinary rocks. Below the surface, however, they’re glimmering with colour.
At Liquidfin, we know our rocks from our gemstones. That’s why we’re the premier place to sell your diamonds, sapphires, and other precious and semiprecious stones. Call us today for more information.
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