Cystals are nature's jewels. Calcite is one of the most common minerals on the earth. The colour is vitreous, white or colourless and may occasionally show phosphorescens or fluorescens. With impurities it can be any colour of the rainbow including gray or black.
Clear Calcite crystals produce double refraction. The best known Calcite is Iceland spar a high quality transparent variety which is known for it's double refraction.
The Cerussite crystals are very pretty but also very brittle. Cerussite is known as white lead, it is a lead ore.