Category: Crystal Habit
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Reniform – Kidney-shaped masses
Common examples include: cassiterite, chalcedony, chrysocolla, hematite, fluorite, goethite, greenockite, malachite, wavellite, mottramite
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Mammillary – Breast-like: surface formed by intersecting partial spherical shapes, larger version of botryoidal and/or reniform, also concentric layered aggregates. It is almost synonymous with reniform.
Common examples include: chalcedony, hematite, malachite
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Botryoidal – Grape-like, large and small hemispherical masses, nearly differentiated/separated from each other
Common examples include: chalcedony, pyrite, smithsonite, hemimorphite A botryoidal (/ˌbɒtriˈɔɪdəl/ BOT-ree-OY-dəl) texture or mineral habit, is one in which the mineral has an external form composed of many rounded segments, named for the Ancient Greek βότρυς (bótrus), meaning “a bunch of grapes“. This is a common form for many minerals, particularly hematite and malachite, which are known for frequently forming botryoidal masses. It is also a common form of goethite, smithsonite, fluorite, and chrysocolla.…
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Tetrahedral – Tetrahedron-shaped, triangular pyramid (four-sided)
Common examples include: tetrahedrite, spinel, sphalerite, magnetite
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Scalenohedral – Scalenohedron-shaped, pointy ends
Common examples include: calcite, rhodochrosite, titanite In crystallography, “regular” right “symmetric” “didigonal” (8-faced) and ditrigonal (12-faced) scalenohedra exist. The smallest geometric scalenohedra have eight faces, and are topologically identical to the regular octahedron. In this case (2n = 2×2), in crystallography, a “regular” right “symmetric” “didigonal” (8-faced) scalenohedron is called a tetragonal scalenohedron.
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Rhombohedral – Rhombohedron-shaped (six-faced rhombi)
Common examples include: calcite, rhodochrosite, siderite
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Pseudo-hexagonal – Hexagon-like appearance due to cyclic twinning
Common examples include: aragonite, chrysoberyl
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Prismatic – Elongate, prism-like: well-developed crystal faces parallel to the vertical axis
Common examples include: beryl, tourmaline, vanadinite, emerald
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Octahedral – Octahedron-shaped, square bipyramid (eight-sided)
Common examples include: diamond, fluorine, fluorite, magnetite, pyrite
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Hexagonal – Hexagonal prism (six-sided)
Common examples include: emerald, galena, quartz, hanksite, vanadinite
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Equant/Stout – Length, width, and breadth roughly equal
Common examples include: apophyllite, olivine, garnet
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Enantiomorphic – Mirror-image habit (i.e. crystal twinning) and optical characteristics; right- and left-handed crystals
Common examples include: gypsum, quartz, plagioclase, staurolite
