A few gemstones are used as gems in the crystal or other form in which they are found. Most of them are cut and polished for usage as gemstones. The two main classifications are stones cut as smooth, dome shaped stones called cabochons, and stones which are cut with a faceting machine by polishing small flat windows called facets at regular intervals at exact angles.

Opaque Stones such as opal, turquoise, etc. are commonly cut as cabochons. They are designed in such a way that they show the stone's color or surface properties as in opal and star sapphires. Grinding, shaping and polishing to the smooth dome shape of the stones  is done with grinding wheels and polishing agents.

Transparent gems are normally faceted, to show the optical properties of the stone’s interior to its best by maximizing reflected light which is known to the viewer as "sparkle". There are many commonly used shapes for faceted stones. Proper cutting of the facets in proper angles is must and it varies depending on the gem's optical properties. 

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