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The Copper Sulphide, Chalcocite, forms three kinds of twins symmetrical to ∞P, {110}, to 4/3P∞̆, {043}, and to 1/2P, {112} respectively. The latter is shown in this figure.

Chalcocite

The Copper Sulphide, Chalcocite, forms three kinds of twins symmetrical to ∞P, {110}, to 4/3P∞̆,…

This figure shows a contact twin of copper, one of the three simplest isometric holohedrons according to the "spinel law".

Copper Contact Twin

This figure shows a contact twin of copper, one of the three simplest isometric holohedrons according…

This illustration shows a solid state where the orientation is only partial, as in the case of twin crystals. Here, the molecules of each horizontal row have two of their axes parallel with those above and below them, but not the third.

Partial Orientation of Molecules in a Solid

This illustration shows a solid state where the orientation is only partial, as in the case of twin…

This figure shows a contact twin of Spinel, one of the three simplest isometric holohedrons according to the "spinel law".

Spinel Contact Twin

This figure shows a contact twin of Spinel, one of the three simplest isometric holohedrons according…

This figure shows a penetration twin of two tetrahedrons, symmetrical to the octohedral face (tetrahedrite).

Tetrahedrite Penetration Twin

This figure shows a penetration twin of two tetrahedrons, symmetrical to the octohedral face (tetrahedrite).

This figure shows a contact twin of Zinc blende, one of the three simplest isometric holohedrons according to the "spinel law".

Zinc blende Contact Twin

This figure shows a contact twin of Zinc blende, one of the three simplest isometric holohedrons according…