why crystallized quartz is coloury?

Answer 1

Because of the presence of other minerals in the silicon dioxide.

Answer 2

Quartz shows color for the same reasons all minerals show color. Usually it is an impurity introduced to the crystal lattice. I've read several answers that said it contained other minerals, but this is not totally true. There are some odd cases where quartz will contain microcrystals of other minerals such as hematite that will give it a colored appearance such as in pseudoamethyst and jasper. Genereally the purple in amethyst, or the orange in citrine are caused by Iron introduced into the crystal structure. Smokey quartz is most likely due to radiation damage causing a collapse in the structure. The actual color is a result of the way light passes through the crystal structure. If an impurity is introduced, or the structure is damaged, the light takes a different path resulting in some sort of diffraction.

Answer 3

because it's acting as a small prism, and light of different wavelengths has different indices of refraction therefore each wavelength is refracted at a slightly different angle when incident upon the crystal at a certain orientation - this seperates the white light into colors, which is what you see. It has nothing to do with impurities in the crystal - the only thing impurities would do is absorb some of the white light and that area would appear to be dark, not colored.

Answer 4

Some , trace minerals etc can cause the quartz to have color Different chemical content will cause different colors
Ameythst , Citrine , some Carnelion, Rose Quartz are among colored quartz types

Answer 5

The color in quartz comes from other minerals such as iron and the way in which the mineral refracts and reflects light.