They are minerals that
have one of the halogen elements as anions.
It is a small group of
Halite by Orbital Joe via Flickr.com
the common table
It forms cubic crystals, or can be massive, compact or
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 by Ron Schott via Flickr.com
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.
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
Atacamite by snaileater via Flickr.com
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
can locally be a minor ore