What is finely ground silica?

Answer 1

Silica mining and manufacturing companies grind the mined ore down to an average particle size ranging from 15 to 3 microns. All of the raw ore is naturally occurring silica that is typically surface mined. The finished product is much finer than industrial sand (e.g., playground sand, Golf sand, filtration sand, etc.). The overall particle size distribution typically falls below a 200 mesh screen or 74 microns. The particle size distribution range is typically between 74 microns down to 5 microns. The finished material is fine in particle size similar to baking flour.

Quartz is the most common silica crystal and the second most common mineral on the earth's surface. It is found in almost every type of rock; igneous, metamorphic and sedimentary. While quartz deposits are abundant, and quartz is present in some form in nearly all mining operations, high purity and commercially viable deposits occur less frequently. Silica sand deposits are most commonly surface-mined in open pit operations, but dredging and underground mining are also employed. Extracted ore undergoes considerable processing to increase the silica content by reducing impurities. It is then dried and sized to produce the optimum particle size distribution for the intended application. {source

http://www.ima-na.org/industrial-sand}