As a general rule, the purer the sand is, the clearer the Glass…

Silica Sand, A Silicon and oxygen are the earth’s two most abundant elements and together they make silica, one of the earth’s three most common rock forming minerals. The chemical compound silica, also known as silicon dioxide, is the oxide of silicon, chemical formula SiO2. Siliceous is an adjective meaning “referring to silica”.

Silica is found in nature in several forms, including quartz and opal. In fact, it has 17 crystalline forms. The most common constituent of sand in inland continental settings and non-tropical coastal settings is silica, usually in the form of quartz because the considerable hardness of this mineral resists erosion. However, the composition of sand varies according to local rock sources and conditions.

Sand is the general term for broken down granules of minerals or rocks, technically between about one-sixteenth of a millimeter to two millimeters in diameter, falling between silt and gravel in the spectrum of sizes.