Sand is Nature's form of Recycling
October 28, 2001

As land-eroding November gales gnaw at the red clay bluffs, it would seem that the beach area should be an ooze of slippery clay. Yet, after the waves have subsided, the wide expanse of sand is still there.

Sand's path to the beach is an interesting one.

First, a definition of sand: When rocks and minerals are broken down, their products may be classified as gravels, sands, silts and clays. When particles range in size from one-twentieth to two millimeters in size, they are classified as sand. Almost all rock making materials might be found in sand, the most common ingredient is quartz.

Chemically, quartz is a compound made up of one part silicon and two parts oxygen. Comparatively hard (it cannot be scratched with a knife, but it scratches glass easily), it is not readily worn down. It is nearly insoluble in water and does not decompose. It is found in igneous rocks, such as granite, in sedimentary rocks in the form of sandstone, and in the metamorphic rock quartzite. A grain of sand, the smallest bit of matter to survive the destruction of quartz-bearing rocks, is practically immortal.

When rocks weather and disintegrate, the quartz and other minerals are eventually washed into streams and lakes. The glacial till that covers this area also contains mixtures of fine to coarsely sorted materials. As these particles are carried toward the lake, some are ground to a fine powder and dropped.

Waves do the final sorting according to weight. Lighter particles and materials, such as feldspars and micas are carried away to be deposited farther from shore.. the heavier ones are washed back upon the beach. This constant sorting goes on, leaving the sand, composed mainly of quartz, on the beach, while other materials are washed away.

Especially strong waves carry coarser sands further up the shore. Like blotting paper, these sands absorb the waves. Out of reach of constant moisture, they become dry and are moved farther inland by wind. When an obstruction is met (driftwood of some hard plant) the wind is slowed down, it drops its load of sand, and a dune is started.

Often a considerable amount of black sand is found along the beach. these particles being much heavier than quartz grains tend to be deposited at the edge of wave scallops where they form conspicuous bands. Most of these grains are magnetite. A magnet, covered with a plastic bag and dragged through these dark areas, will soon yield a quantity of magnetic material. Putting an uncovered magnet into the sand results in a magnet loaded with fine dust that is practically impossible to remove.

Magnetite is an iron ore. Although this would seem to be a valuable source of iron, it has been analyzed and found that with present knowledge it would not be an economical resource. It is used in the U.S. Senate as ink-blotting sand.

Sand is a valuable resource. It is the main constituent in glass, it is used in making foundry molds, as well as for abrasives, mortar and concrete.

Sand from weathered igneous rocks become sandstone. Sandstone becomes quartzite. These rocks, in turn are again eroded into sand. Recycling is nothing new to Mother Nature.