Diatomaceous Earth is not Beach Sand

The most common constituent of sand, in inland continental settings and non-tropical coastal settings, is silica (silicon dioxide, or SiO2), usually in the form of quartz, which, because of its chemical inertness and considerable hardness, is the most common mineral resistant to weathering.

Beach Sand is typically made mostly of varying amounts of material weathered from inland rocks (or sea cliff material) and transported to the beach on the wind or in rivers, and/or shells and other hard parts precipitated out of the ocean water by marine organisms.

Localities such as the tropical islands of Hawaii have volcanic rocks that have little quartz but lots of feldspar. Most are made of carbonate sands (fragments of coral and mollusk shells and tiny micro-organisms called foraminifera) that are derived within the surf zone by erosion of the surrounding reefs. Some of the other tropical beaches are black sands that form in beach pockets and are composed of glassy volcanic debris. 

What is Quartz?

Quartz is a hard white or colorless mineral consisting of silicon dioxide, found widely in igneous, metamorphic, and sedimentary rocks. It is often colored by impurities (as in amethyst, or citrine).

What is Diatomaceous Earth made of?

Diatomaceous earth is made from the fossilized remains of tiny, aquatic organisms called diatoms. Their skeletons are made of a natural substance called silica. The formula is also silicon dioxide, or SiO2. Over a very long period of time, diatoms accumulated in the sediment of rivers, streams, lakes, and oceans. Today, silica deposits are mined from these areas.

What are Seashells made of?

Seashells are composed mostly of calcium carbonate. (Formula CaCO3), and a small amount of protein