Glittering Stones >> Crystal Habit

Crystal habit

In mineralogy, shape and size give mount to evocative terms applied to the typical appearance, or habit of crystals

The many terms used by mineralogists to explain crystal habits are very useful in communicating what specimens of a meticulous mineral frequently look like. Recognizing numerous habits helps a mineralogist to recognize a large number of minerals. Some habits are characteristic of certain minerals, although the majority minerals exhibit many conflicting habits which are influenced by certain factors. Crystal habit might mislead the inexperienced as a mineral's crystal system could be hidden or even disguised.

Factors influence a crystal's habits include: a combination of two or even more forms; trace impurities there during growth; crystal twinning and growth conditions (i.e., heat, pressure, space). Minerals feel right to the same crystal system do not necessarily exhibit the same habit. Some habits of a stone are exclusive to its variety and locality: For example, while most sapphires form elongate barrel-shaped crystals, those establish in Montana form stout tabular crystals. Ordinarily, the latter habit is seen only in ruby. Sapphire and also ruby are both varieties of the same mineral; corundum.

Some minerals might replace other obtainable minerals while preserving the original's habit: this procedure is called pseudomorphous replacement. A classic example is tiger's eye quartz, crocidolite asbestos restored by silica. While quartz typically forms ethereal (well-formed), prismatic (elongate, prism-like) crystals, in tiger's eye the unique fibrous habit of crocidolite is preserved.