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This is a crystal of Copper Silicate (Dioptase) with a rhombohedron of the third order, (s), in combination with the prism of the second order, (m), and the negative rhombohedron, (r). This crystal is an example of rhombohedral tetartohedrism in the hexagonal system.

Copper Silicate Showing Rhombohedral Tetartohedrism In the Hexagonal System

This is a crystal of Copper Silicate (Dioptase) with a rhombohedron of the third order, (s), in combination…

"...represents a crystal of dioptase with the fundamental rhombohedron (r) and the hexagonal prism of the second order (m) combined with the rhombohedron (s)." -The Encyclopedia Britannica 1910

Crystal of Dioptase

"...represents a crystal of dioptase with the fundamental rhombohedron (r) and the hexagonal prism of…