Reniform – Kidney-shaped masses
Common examples include: cassiterite, chalcedony, chrysocolla, hematite, fluorite, goethite, greenockite, malachite, wavellite, mottramite
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
Globular – Isolated hemispheres or spheres
Common examples include: calcite, fluorite, gyrolite
Colloform – Rounded, finely banded
Common examples include: sphalerite, pyrite
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 min
Tetrahedral – Tetrahedron-shaped, triangular pyramid (four-sided)
Common examples include: tetrahedrite, spinel, sphalerite, magnetite
Scalenohedral – Scalenohedron-shaped, pointy ends
Common examples include: calcite, rhodochrosite, titanite In crystallography, “regular” right “symmetric” “didigonal” (8-faced) and ditrigona
Rhombohedral – Rhombohedron-shaped (six-faced rhombi)
Common examples include: calcite, rhodochrosite, siderite
Pseudo-hexagonal – Hexagon-like appearance due to cyclic twinning
Common examples include: aragonite, chrysoberyl
Prismatic – Elongate, prism-like: well-developed crystal faces parallel to the vertical axis
Common examples include: beryl, tourmaline, vanadinite, emerald
Octahedral – Octahedron-shaped, square bipyramid (eight-sided)
Common examples include: diamond, fluorine, fluorite, magnetite, pyrite
Icositetrahedral – Icositetrahedron-shaped, 24-faced
Common examples include: spessartine
Hexagonal – Hexagonal prism (six-sided)
Common examples include: emerald, galena, quartz, hanksite, vanadinite
Equant/Stout – Length, width, and breadth roughly equal
Common examples include: apophyllite, olivine, garnet
Enantiomorphic – Mirror-image habit (i.e. crystal twinning) and optical characteristics; right- and left-handed crystals
Common examples include: gypsum, quartz, plagioclase, staurolite
Dodecahedral – Dodecahedron-shaped, 12-sided
Common examples include: garnet, pyrite