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2 Brittle at room temperatures.

3 Quite soluble in polar substances (such as water).

4 Intermediate melting temperatures.

5 Absorb relatively small amounts of light, producing translucent to transparent minerals with light colors and vitreous to sub‐vitreous luster in macroscopic crystals.

covalent bondselectron‐sharing bonds

ssss1 Relationship between attractive and repulsive forces between ions produces a minimum net force when the near spherical surfaces of the ions are in contact.

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ssss1 (a) Covalent bonding (double lines) in a carbon tetrahedron with the central carbon atom bonded to four carbon atoms that occupy the corners of a tetrahedron (dashed lines). (b) A larger scale diamond structure with multiple carbon tetrahedra.

Source: Courtesy of Steve Dutch.

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Covalently bonded minerals are generally characterized by the following:

1 Hard and brittle at room temperature.

2 Insoluble in polar substances such as water.

3 Crystallize from melts.