Minerals, Rocks, Crystals & Gems

Mineral: nature's building block

A mineral is a naturally occurring, inorganic solid with a specific chemical composition and an orderly internal atomic structure. Quartz (SiO₂) and halite (NaCl) are minerals: each has a fixed recipe and a repeating atomic lattice. There are roughly 6,000 known minerals, but only a few dozen are common.

Rock: a mixture of minerals

A rock is an aggregate — a naturally bonded mixture of one or more minerals (plus, sometimes, glass or organic matter). Granite is a rock made of quartz, feldspar, and mica grains locked together. Because it's a mixture, a rock has no single chemical formula. Think of minerals as ingredients and rocks as the finished dish.

Crystal: mineral with room to grow

A crystal is simply a mineral whose atoms had the time and space to arrange into a well-formed geometric shape, with flat faces and sharp edges. The same quartz that forms shapeless masses can, given an open cavity, grow into gorgeous six-sided points. 'Crystal' describes form, not a separate substance.

Gem: beauty meets rarity

A gem (or gemstone) is a mineral — occasionally a rock like lapis lazuli, or an organic material like amber or pearl — that is beautiful and durable enough to be cut and worn. 'Gem' is a cultural and commercial label about desirability, not a scientific class. A ruby is gem-quality corundum; ordinary corundum is just a mineral. Value comes from color, clarity, cut, and carat weight.

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