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A form of silicate that is found in great abundance throughout Europe. It is white and can be scratched with the nail. Alabaster was used to craft anything from vases to perfume boxes.

Alabaster

A form of silicate that is found in great abundance throughout Europe. It is white and can be scratched…

This figure reproduces a combination of orthorhombic forms observed on crystals of aluminum orthosilicate, or Andalusite: (a), (b), (c), (m), (l), (n), (r), (p), (s), and (k).

Andalusite

This figure reproduces a combination of orthorhombic forms observed on crystals of aluminum orthosilicate,…

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…

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…

Hemimorphite is a sorosilicate mineral consisting of hydrous zinc silicate.

Hemimorphite

Hemimorphite is a sorosilicate mineral consisting of hydrous zinc silicate.

This figure exhibits a combination occurring on the ferro-magnesian meta-silicate, Hypersthene. Forms: (a), (b), (m), (n), (h), (o), (c), (i), and (u).

Hypersthene

This figure exhibits a combination occurring on the ferro-magnesian meta-silicate, Hypersthene. Forms:…

This figure shows a crystal of Orthoclase, exhibiting forms (M), (P), (T), (x), (y), (o), and (n).

Orthoclase

This figure shows a crystal of Orthoclase, exhibiting forms (M), (P), (T), (x), (y), (o), and (n).

An alternate combination of manganese meta-silicate (Rhodonite), showing forms: (c), (b), (a), (n), (h), (o), and (s).

Rhodonite

An alternate combination of manganese meta-silicate (Rhodonite), showing forms: (c), (b), (a), (n),…

This figure shows a combination of forms sometimes observed on the silicate Scapolite, with the unit pyramid, (o); the prisms of the first and second orders, (M) and (b) respectively; and the pyramid of the third order, (s).

Scapolite

This figure shows a combination of forms sometimes observed on the silicate Scapolite, with the unit…

Striation of crystal planes may be produced by repeated polysynthetic twinning. This is well illustrated in the case of the triclinic feldspar, Albite. The twinning plane here is the brachypinacoid, and the contact of a large number of fine lamellæ, alternately in twinning position, would evidently produce a striation on the basal plane parallel to the brachydiagonal axis

Striation of Crystal Planes

Striation of crystal planes may be produced by repeated polysynthetic twinning. This is well illustrated…

This crystal of Tourmaline exhibits hemimorphism in the direction of the vertical axis. Its forms are the prisms, (g), which as a result of hemimorphism, appear as a trigonal prism, and (a); the scalenohedron, (s), and the two rhombohedrons, (R) and (r), at the antilogue pole, while only (R) occurs at the analogue pole.

Tourmaline

This crystal of Tourmaline exhibits hemimorphism in the direction of the vertical axis. Its forms are…