"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different forms have been described." — Ford, 1912

Calcite

"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…

"Hexagonal-rhombohedral. Crystals usually prismatic in habit or tapering hexagonal pyramids." — Ford, 1912

Corundum

"Hexagonal-rhombohedral. Crystals usually prismatic in habit or tapering hexagonal pyramids." —…

"Hexagonal-rhombohedral. Crystals usually prismatic in habit or tapering hexagonal pyramids." — Ford, 1912

Corundum

"Hexagonal-rhombohedral. Crystals usually prismatic in habit or tapering hexagonal pyramids." —…

"Hexagonal-rhombohedral. Crystals usually thick to thin tabular. Basal planes prominent, often showing triangular markings." — Ford, 1912

Hematite

"Hexagonal-rhombohedral. Crystals usually thick to thin tabular. Basal planes prominent, often showing…

"Hexagonal-rhombohedral. Crystals usually thick to thin tabular. Basal planes prominent, often showing triangular markings." — Ford, 1912

Hematite

"Hexagonal-rhombohedral. Crystals usually thick to thin tabular. Basal planes prominent, often showing…

"Hexagonal-rhombohedral. Crystals usually thick to thin tabular. Basal planes prominent, often showing triangular markings. Edges of plates sometimes beveled with rhombohedral and pyramidal forms." — Ford, 1912

Hematite

"Hexagonal-rhombohedral. Crystals usually thick to thin tabular. Basal planes prominent, often showing…

"The vertical crystallographic axis is one of trigonal symmetry, and the three horizontal crystallographic axes of binary symmetry." — Ford, 1912

Symmetry of Rhombohedral Class

"The vertical crystallographic axis is one of trigonal symmetry, and the three horizontal crystallographic…

"...in this figure the thicker lines are the projections of the three planes of symmetry, and on these lie the poles of the rhombehedra (six of which are indicated)." -The Encyclopedia Britannica 1910

Stereographic Projection of a Holosymmetric Rhombohedral Crystal

"...in this figure the thicker lines are the projections of the three planes of symmetry, and on these…