It is natural mineral abrasive that appears in many forms everywhere on Planet Earth.
Quartz is one of the common minerals that could be found everywhere. Its formula is silicon dioxide or SiO. Pieces of quartz in nature may have different shape and color. Usually it is colorless or white but it may have great variety of colors like:
– Rock crystal (colorless)
– Milky (white)
– Rose (milky pink)
– Amethyst (purple)
– Citrine (yellow)
– Prasiolite (green)
– Smoky (grey)
– Cairngorm (brown)
– Morion (black)
There is also so called Herkimer diamond, named after its specific natural crystal form.
Quartz is tough and inert mineral and has hardness of 7 on the Mohs scale, so it can successfully scratch glass and metals and could be used as abrasive. It could be found mostly in light-colored rocks or sandstones.
Quartz is everywhere. In fact most of what we call sand is grains of quartz. It is also the basic content of granite. Very small in size in granite and sand rocks, in plutonic rocks quarts crystals grow to very solid forms.
The cheapest sandpaper is made from sand /quartz grains/ and it has enough hardness to work on wood. It scratches the surface to make it smoother or polish it but it can not shape the material. This make it part of Abrasive Minerals family.