Brighter than a diamond

What are some rare photos of raw, rough and uncut gemstones?

Sphene, also known as Titanite, is a rare collector gemstone with an unusually high refractive index, noted for strong trichroism when the three colors presented being dependent on body color. This gemstone features "fire" phenomena, - the special effect due to dispersion and refers to the ability of the gemstone to draw light apart into its constituent colors. This works just like the glass prism that unfolds sunlight into the rainbow by refraction.