Halides
"Halides
are minerals
that have one of the halogen elements as anions."
Halite
Halite is the common table salt, NaCl. It forms cubic crystals, or can be massive, compact or granular. It is most often white when pure, but can also be coloured by impurities and be purpleish, reddish, yellowish, orange or colourless. It is an evaporate mineral that forms when water evaporates.
Sylvite
Sylvite is potassium chloride - another evaporate that forms when water evaporates. Like halite is forms cubic crystals or granular masses. It is white or colourless when pure, but can be coloured by impurities to be red, purple, yellow or blue. While halite has a salty taste, the taste of sylvite's is bitter.
Fluorite
Fluorite's anion is fluorine - another common halogen element. It forms crystals but can also be compact, granular or massive. It can come in many colours but is most often purple, green or yellow. It is known as a gemstone and is widely used in many industries. It often forms in hydrothermal veins with silver and lead ores, but is also found in pegmatites and sedimentary rocks.
Atacamite
Atacamite's formula is a bit more complicated, it contains copper, chloride and hydroxide. Its colour varies from dark to bright green. It forms tabular or slender crystals, or can be fibrous, granular or massive. It is formed as a secondary mineral when copper oxidises, in association with azurite and malachite. It can locally be a minor ore of copper.
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