The various shapes that crystals form in are referred to as 'habits'. Habit can also refer to the manner in which a number of crystals are grouped together and and the arrangement of masses of crystalline material which does not show obvious crystal forms.

Crystal habits include the following;

• Cubic or Octahedral Habit refers to well developed minerals which crystallise in the isometric or cubic system.
• Prismatic Habit refers to crystals that are taller than they are wide. Depending on their lengths they may be referred to as long or short prismatic.
• Tabular Habit refers to flat crystals (table-top or book shape).
• Pyramidal Habit  refers to a prismatic crystal where a number of faces terminate at a mutual meeting point.
• Dipyramidal Habit is where both the top and bottom of a crystal are capped by pyramids.
• Columnar Habit is when the length of a prismatic crystal greatly exceeds it's width.
• Acicular Habit is when the columns are very slender, like a match or needle.
• Fibrous Habit is when they are even thinner, like a thread.
• Capillary Habit is when the crystals are very delicate & hair-like.
• Bladed Habit refers to a crystal which is long & wide but very thin, like a knife blade.

The above habits may occur as either individual crystals  or as groups where the crystals are parallel or sub-parallel to each other. Other arrangements include;

• Reticulated Habit which is the criss-cross patterns of a group of slender crystals.
• Radiated Habit where a number of long crystals radiate from a common centre.
• Foliated, Lamellar, or Micaceous Habits where the minerals can be split into thin sheets.
• Rosetted Habit where the crystals are arranged like the petals on a rose.

Other types of habits are wire-like. These include;

• Branching Habit, commonly known as Dendritic or tree-like.
• Coralloidal Habit describing minerals with a coral-like growth.

Aggregates of crystalline material also produce a variety of arrangements. These are minerals which crystallise as masses with regular or irregular rounded surfaces, but usually with an inner radial structure. These habits are known as 'Colloform' and there are a number of variations;

• Botryoidal Habit refers to the bulls-eye appearance of some malachite or chalcedony.
• Mamillary Habit is when the rounded protuberances are larger.
• Reniform Habit is when the protuberances are more kidney-shaped.
• Globular Habit is when the projections are more or less spherical.
• Concentric Habit refers to minerals made up of circular layers arranged around a centre.
• Oolitic Habit is where minerals form small spherical bodies similar to fish-roe.
• Pisolitic Habit is when the spheres are larger, the size of peas.
• Nodular Habit is when the spherical bodies are more irregular.
  

Small or microscopic crystal habits include;

• Drusy Habit which is when a large number of minute crystals inhabits the surface of an object. Also known as 'encrustation', this commonly occurs in cavities and veins.
• Granular Habit which is when a mineral is composed of an aggregate of very small grains.
  

A mineral is termed 'crypto-crystalline' if the crystals are too small to be seen even under an ordinary microscope.

Finally there are a very small number of minerals which have no crystalline structure at all. These are known as 'Amorphous' or 'Massive'. An example of this is obsidian.