Calamine
"The only orthorhombic mineral of importance belonging to the hemimorphic class is calamine. When its…
Calamine
"Orthohombic, hemimorphic. Crystals usually tabular parallel to the brachypinacoid. They show prism…
Calcite
"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…
Calcite
"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…
Calcite
"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…
Calcite
"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…
Calcite
"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…
Carboniferous Landscape
The continents during this age consisted mainly of large, flat, marshy areas, covered with luxuriant…
Cassiterite
"Tetragonal. Common forms are prisms and pyramids of first and second orders." — Ford, 1912
Cave
An illustration of a cliff with with a cave. A cave is a natural underground void large enough for a…
Celestite
"Orthorhombic. Crystals resemble closely those of barite. Commonly tabular parallel to the base or prismatic…
Symmetry center
"A crystal has a center of symmetry if an imaginary line is passed from some point on its surface through…
Cerussite
"Habit varied and crystal show many forms. Crystals often tabular parallel to brachypinacoid." —…
Chabazite
"Hexagonal-rhombohedral. Common form is the simple rhombohedron, r, having nearly cubic angles. May…
Chalcocite
"Orthorhombic. Usually in small tabular crystals with hexagonal outline. Striated parallel to the brachy-axis."…
Chalcocite
"Orthorhombic. Usually in small tabular crystals with hexagonal outline. Striated parallel to the brachy-axis.…
Columbite
"Orthohombic. Habit of crystals is short prismatic; often in square prisms because of prominent development…
Coral Island
The reef forming the island is of limestone, derived form countless skeletons of minute polyps that…
Coral Polyp
"Part of a branch of a coral of the genus Gorgonia, showing one of the polyps expanded." -Dana, 1883
Fossil Coral
Favosites alcyonaria is a species of fossil corals from the Silurian, Devonian, and Carboniferous strata.
Corundum
"Hexagonal-rhombohedral. Crystals usually prismatic in habit or tapering hexagonal pyramids." —…
Corundum
"Hexagonal-rhombohedral. Crystals usually prismatic in habit or tapering hexagonal pyramids." —…
Sulphur crystal
"The forms present upon it are two pyramids of different slope but each intersecting all three of the…
Cube and pyritohedron
"A combination of cube and pyritohedron, in which it will be noted that the faces of the pyritohedron…
Cube and tetrahedron
"A combination of cube and tetrahedron. It will be noted that the tetrahedron faces truncate the alternate…
Cube and tetrahexahedron
"A cube with its edges beveled by the faces of a tetrahexahedron." — Ford, 1912
Cube, dodecahedron and tetrahedron
"A combination of cube, dodecahedron, and tetrahedron." — Ford, 1912
Octahedron trunctuated by cube
"When a corner or an edge of one form is replaced by a face of another form, the first is said to be…
Twinned cubes
"A penetration twin, since the two individuals interpenetrate each other." — Ford, 1912
Cyclonema Mollusk
A mollusk radiate from the Paleozoic time, Cyclonema cancellata from the Clinton group.