Fluorite,

very often occurring mineral from the mineral class of simple halides. Pure fluorite is colorless and transparent. It can take almost all colors by foreign admixtures. Frequently common are e.g. green, violet and yellow crystals.

Opal,

often occurring mineral from the mineral class of oxides and hydroxides. As an amorphous solid opal has no crystalline structure and usually occurs as massive vein filling or bulbous formed.