The genesis of silica sand is associated with a large number of factors, including its chemical and physical properties.

That is where you can get silica /quartz, tridymite... from

(1)Magmatic deposits

(1)Agate-amethyst-rock-crystal-opal deposits in basic to acidic volcanic rocks

(1)Hypogene agate-amethyst-rock crystal-opal deposits in basic magmatic rocks (40a B)

(2)Thundereggs in felsic magmatic rocks (40a D)

(3)Supergene opal deposits on top of basic and felsic magmatic rocks (40b B-40b H)

(4)Hypogene zeolite-celadonite-bearing opal deposits in basic to acidic magmatic rocks (40f BCD)

(2)Opal and quartz in volcanic sinter, geyserites and high-sulfidation replacement deposits (40c CD)

(3)Quartz- and semi-precious gemstone pegmatites (40 dD)

(4)Glass-bearing pyroclastic and volcanic rocks

(1)Pumice (40g CDE)

(2)Scoria (40g B)

(3)Perlite (40h CD)

(2)Structure-related deposits

(1)Unconformity-related shallow quartz veins (40a G)

(2)Deep-seated lineamentary quartz veins (40c G)

(3)Sedimentary deposits

(1)Silcretes

(1)Quartz (40a H)

(2)Chalcedony (40c H)

(3)Opal (40d H)

(2)Rock crystal placers (40a I)

(3)Quartz sandand arenites (40c I)

(4)Limnoquartzite (transitional into volcano-sedimentary deposits) (40e J)

(5)Biogenic silica deposits

(1)Diatomite (40c J)

(2)Radiolarite (40d J)

(3)Chert (40g J)

(4)Rottenstone/ tripolite (40c K)

(4)Metamorphic deposits

(1)(Meta)quartzites (40d I)

(2)Opal concretions in graphite schist (40h J)

(3)Onyx within marble (40d K)

(4)Tektites (40a N)

(5)Zebra rock (40a J)

from the Chessboard classification scheme (Dill 2010)

For quartz sand of high purity you need

1. intensive chemical and mechnical weathering to separate wheat from chaff

2. Muliple recycling in marine and fluvial aquatic systems

HGD