Illustrated · 1 min
Note: If you find a mineral in a certain shape, it does not necessarily mean that shape is it's crystal habit.
Crystal Habit of minerals is the general shape it takes as a pure crystal. Tourmaline crystals, for example, grow in a prismatic way. Crystal Habits include:
Blocky/Equant: The mineral is roughly box-like or ball-like.
Tabular: The mineral is shaped thin but long, like a deck of cards or a sheet of paper.
Prismatic: The mineral is shaped like a prism. (Hmm...) The mineral is long compared to it's width and the bases are parallel.
Bladed: Long thin crystals, which would be flattened like a knife.
Acicular: The crystal is shaped like a needle.
In mineral habits, mineral habits can also be distinguished by how the crystals are grouped together. For example, different minerals can be separated by how groups of distinct crystals are, how parallel or radiating clusters are, how a group of crystals that are flaky or scaly are, and even others. Simply, crystal habits is the way the crystal is shaped.
To distinguish your mineral based on crystal habits go to: http://www.minsocam.org/msa/collectors_corner/id/mineral_id_keyi8.htm
Millerite has an acicular crystal habit.