Shipworms, termites of the sea
The shipworms are marine bivalve molluscs in the family Teredinidae: a group of saltwater clams with long, soft, naked bodies. They are notorious for boring into (and commonly eventually destroying) wood that is immersed in sea water, including…
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
Botryoidal – Grape-like, large and small hemispherical masses, nearly differentiated/separated from each other
Common examples include: chalcedony, pyrite, smithsonite, hemimorphite A botryoidal (/ËbÉtriËÉÉȘdÉl/ BOT-ree-OY-dÉl) texture or mineral habit, is one in which the mineral has an external form composed of many rounded segments, named for the Ancient Greek ÎČÏÏÏÏ Ï (bĂłtrus), meaning “a bunch of grapes“.…
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 ditrigonal (12-faced) scalenohedra exist. The smallest geometric scalenohedra have eight faces, and are topologically identical to the regular octahedron. In…
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



Kidney-shaped masses">



Tetrahedron-shaped, triangular pyramid (four-sided)">



Octahedron-shaped, square 




