Recognizing the habit can aid in mineral identification and description, as the crystal habit is an external representation of the internal ordered atomic arrangement.[1] Most natural crystals, however, do not display ideal habits and are commonly malformed. The quality of the shape of a crystal in a mineral specimen can be described as one of the following:
Factors influencing habit include: a combination of two or more crystal forms; trace impurities present during growth; crystal twinning and growth conditions (i.e., heat, pressure, space); and specific growth tendencies such as growth striations. Minerals belonging to the same crystal system do not necessarily exhibit the same habit. Some habits of a mineral are unique to its variety and locality: For example, while most sapphires form elongate barrel-shaped crystals, those found in Montana form stout tabular crystals. Ordinarily, the latter habit is seen only in ruby. Sapphire and ruby are both varieties of the same mineral: corundum.
Some minerals may replace other existing minerals while preserving the original's habit, i.e. pseudomorphous replacement. A classic example is tiger's eye quartz, crocidolite asbestos replaced by silica. While quartz typically forms prismatic (elongate, prism-like) crystals, in tiger's eye the original fibrous habit of crocidolite is preserved.
| Habit
| Image
| Description
| Common example(s)
|
| Acicular
| | Needle-like, slender, and end-tapered prisms growing in a radial/globular fashion.
| natrolite, scolecite, yuanfuliite
|
| Arborescent
| | Tree-like crystals growing similar to branches.
| Native copper, gold, native silver
|
| Capillary/Filiform
| | Hair-like or thread-like, extremely fine
| byssolite, millerite
|
| Colloform/Nodular/Tuberose
| | Rounded, finely banded deposits with irregular concentric protuberances
| agate, baryte, sphalerite
|
| Concentric
| | Circular ring aggregates around a center. This habit is found in cross-sections from reniform/mamillary habits, and also from elongated stalactites of amethyst (quartz), malachites, rhodocrosite, and others
| agate, quartz, malachite, rhodocrosite
|
| Dendritic
| | Root-like, branching in one or more direction from central point
| Native copper, gold, romanechite, magnesite, native silver
|
| Druse/Encrustation
| | Aggregate of crystals coating a surface or cavity, usually found in geodes and some fossils | azurite, celestine, calcite, uvarovite, malachite, quartz |
| Fibrous/Asbestiform
| | Extremely slender prisms forming muscle-like fibers
| actinolite, asbestos, baryte, kyanite, gypsum, nitratine, stilbite, serpentine group
|
| Foliated/Micaceous/Lamellar
| | Layered crystal planes, parting into thin sheets
| biotite, hematite, muscovite, lepidolite, molybdenite
|
| Granular
| | Aggregates of diminute anhedral crystals in matrix or other surface
| andradite, bornite, scheelite, quartz, uvarovite
|
| Hopper
| | Outer portions of cubes grow faster than inner portions, creating a concavity similar to that of a hopper
| bismuth (artificial), halite, galena |
| Oolithic
| | Small spheres or grains (commonly flattened) that resemble eggs
| aragonite, calcite |
| Pisolitic
| | Rounded concentric nodules often found in sedimentary rocks. Much larger than oolithic
| aragonite, bauxite, calcite, pisolite
|
| Platy/Tabular/Blocky
| | Flat, tablet-shaped, prominent pinnacoid
| baryte, feldspar, topaz, vanadinite, wulfenite
|
| Plumose
| | Fine, feather-like scales
| aurichalcite, okenite, mottramite
|
| Radial/Radiating/Divergent
| | Radiating outward from a central point without producing a star (crystals are generally separated and have different lengths).
| aenigmatite, atacamite, epidote, pyrophyllite, stibnite
|
| Reticulated
| | Crystals forming triangular net-like intergrowths.
| cerussite, rutile |
| Rosette/Lenticular
| | Platy, radiating rose-like aggregate (also lens shaped crystals)
| gypsum, baryte, calcite |
| Stalactitic
| | Forming as stalactites or stalagmites; cylindrical or cone-shaped. Their cross-sections often reveal a "concentric" pattern
| calcite, chalcedony, chrysocolla, goethite, malachite, romanechite
|
| Stellate
| | Star-like, radial fibers found inside spherical habits, such as mamillary or reniform.
| hematite, pectolite, shattuckite, wavellite
|
| Habit
| Image
| Description
| Common example(s)
|
| Cubic
| | Cube-shaped
| fluorite, pyrite, galena, halite |
| Dodecahedral
| | Dodecahedron-shaped, 12-sided. Central facet can vary.
| garnet, pyrite |
| Enantiomorphic
| | Mirror-image habit (i.e. crystal twinning) and optical characteristics; right- and left-handed crystals
| aragonite, gypsum, quartz, plagioclase, staurolite
|
| Hexagonal
| | Hexagonal prism (six-sided)
| beryl, galena, quartz, hanksite, vanadinite |
| Icositetrahedral
| | Icositetrahedron-shaped, 24-faced
| analcime, spessartine
|
| Octahedral
| | Octahedron-shaped, square bipyramid (eight-sided)
| diamond, fluorine, fluorite, magnetite, pyrite |
| Prismatic
| | Elongate, prism-like: may or not present well-developed crystal faces parallel to the vertical axis
| beryl, tourmaline, vanadinite |
| Rhombohedral
| | Rhombohedron-shaped (six-faced rhombi)
| calcite, magnesite, rhodochrosite, siderite
|
| Scalenohedral
| | Scalenohedron-shaped, pointy ends
| calcite, rhodochrosite, titanite
|
| Tetrahedral
| | Tetrahedron-shaped, triangular pyramid (four-sided)
| chalcopyrite, tetrahedrite, sphalerite, magnetite |
| Habit
| Image
| Description
| Common example(s)
|
| Botryoidal
| | Grape-like, large and small hemispherical masses, nearly differentiated/separated from each other
| calcite, chalcedony, halite, plumbogummite, smithsonite
|
| Globular
| | Isolated hemispheres or spheres
| calcite, fluorite, gyrolite
|
| Mammillary
| | Breast-like: surface formed by intersecting partial spherical shapes, larger version of botryoidal and/or reniform, also concentric layered aggregates.
| chalcedony, hematite, malachite |
| Reniform
| | Irregular kidney-shaped spherical masses
| cassiterite, chalcedony, chrysocolla, hematite, hemimorphite fluorite, goethite, greenockite, malachite, rhodochrosite, smithsonite, mottramite, wavellite
|