Why do crystals, like quartz and diamonds, form in different colors?

Question

Some crystals, like quartz and diamonds, form in a variety of different colors. For example, quartz can be clear, 'foggy', pink, yellow, and even blue. - What happens during the crystal's formation to make it one color or another?

Answer 1

The reason minerals like quarts and diamonds vary in color is generally caused by the chemical elements involved while the crystal is being formed. Amethyst for example has traces of iron built into its crystalline structure giving it a purple hue (Rogers, 2014).

Chemicals

Different colors can be created by different chemicals. Amethyst for example has traces of iron built into its crystalline structure giving it a purple hue. Iron can also give crystals a yellow hue.

Growth Imperfections

Some colors, like in smoky quartz, are from growth imperfections. These imperfections change the way the crystal reflects light, which changes the appearance of coloration.

Light

Part of the color seen when looking at a crystal is light. When light enters a crystal its spectrum is broken apart, and part of it is absorbed while other parts are reflected. This changes the apparent color of the crystal.what basically happens is that different metal cations (positively charged atoms) in a crystalline structure absorb different wavelengths of light. The identity of the metal is not the only important thing: a paramount factor is the number of oxygen atoms that surround the metal atoms and their shape (be it a tetrahedron, octahedron, etc.) These metals are not part of of the formal chemical composition of the mineral. Instead, they replace other atoms in the mineral by very little amounts. For example, ruby is a mineral composed of aluminum oxide. If you take just a bit of this aluminum and replace it with chromium (less than 1% is enough), it becomes vivid red. Note that in contrast to inclusions, we are talking about different metals in the same mineral, and not inclusions of different minerals (Gimelist, 2014).