Most gemstones are actually mineral crystals (except for non-mineral gems like pearls, coral and amber). Mineral crystals form through a naturally occurring combination of chemicals, heat and/or pressure. These chemicals affect shapes and color of the crystals. Most mineral crystals are tiny, but a few can be cut into gemstones of rare beauty.

a pretty big problem if it gets chipped or scratched

A glass compound with mineral additives that underwent heat treatment to give it hardness, and highly scratch resistant.

This watch crystal, or dial face, is made of a mineral substance that is harder and more durable than an acrylic watch crystal.

Watch crystal made from what is essentially a form of glass. More scratch resistant than acrylic , a mineral crystal will however scratch and is extremely difficult to polish.