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This crystal of Calcium Phosphate, Apatite, represents a complex combination of hexagonal hemihedral forms produced by the pyramidal selection. The nine forms comprise the basal pinacoid ,(P); the prism of the first order, (M); second order, (u); and third order, (h); three pyramids of the first order, (r), (x), and (y); one pyramid of the second order, (s); and one of the third order, (m).

Calcium Phosphate, Apatite

This crystal of Calcium Phosphate, Apatite, represents a complex combination of hexagonal hemihedral…

Also known as Diopside, this crystal exhibits symbols whose forms are: (c), (b), (a), (m), (o), and (u).

Calcium-Magnesium Metasilicate

Also known as Diopside, this crystal exhibits symbols whose forms are: (c), (b), (a), (m), (o), and…

In some cases, the elongation of a crystal may be in the direction of the orthogonal axis, whose position is determined by the plane of symmetry. This crystal of the silicate mineral, Epidote, shows an example of this.

Elongation in the Direction of the Orthogonal Axis

In some cases, the elongation of a crystal may be in the direction of the orthogonal axis, whose position…

Certain crystals of green fluorspar from Saxony, showing the form ∞ 03, {310}, have one half of their planes developed at the expense of the other half, so as to produce a hexagonal scalenohedron.

Green Fluorspar from Saxony

Certain crystals of green fluorspar from Saxony, showing the form ∞ 03, {310}, have one half of their…

"Metallic calcium is prepared by passing an electric current through fused calcium chloride contained in a cruicible of graphite, which acts as the anode." -Brownlee 1907

Metallic Calcium Preparation

"Metallic calcium is prepared by passing an electric current through fused calcium chloride contained…

"A small cylinder of lime is heated to intense luminosity in the flame of a spirit lamp through which a jet of oxygen plays." —The Encyclopedia Britannica, 1903

Oxy-calcium Lamp

"A small cylinder of lime is heated to intense luminosity in the flame of a spirit lamp through which…