Even though it is simple for most people to visualize sand (and they will likely picture something similar), it is by no means a specific substance. Sand is a fine granular material that can be composed of a variety of substances. According to ASTM D2419-14 - Standard Test Method for Sand Equivalent Value of Soils and Fine Aggregate, the term sand refers to “particles of rock that will pass the 4.75 mm (No. 4) sieve and be retained on the 0.075 mm (No. 200) sieve.” While the exact size specification can vary between standards, this still gives a good representation of the size of a grain of sand.
Essentially, sand is the material leftover after rocks breakdown over hundreds of thousands and even millions of years. Some rocky minerals do not decompose easily and, as a result, stay behind for an extended period after they become weathered. For example, one of the most common beach compositions is quartz sand with some feldspar, both of which materials are harder and more resistant than most abundant minerals. This prevalent composition has left most beaches with a light brown complexion.
However, each beach is a composition of its local environment, with regional influences, so it is practically always different and actually indicative of the area in which it is located. For example, in the Florida panhandle, sand is often white because of its high quartz content. Interestingly, in the beaches not too far away around Miami, the beaches are also white, not because of a quartz-heavy composition, but from a buildup of calcium bicarbonate, the molecule that comprises the shells on marine life. Beaches in Hawaii are almost drastically different from these other two, as the dark volcanic rock has left the beaches with black sand.
Most beach sand is rather old, having formed about 5,000 years ago, which can be directly attributed to recent geologic history. About 11,700 years ago, the Earth departed its last Ice Age and continued into the Holocene. From the melted glaciers that once stood over today’s continents, water flooded former river valleys and initiated the formation of estuaries, or bodies of water that are comprised of a mixture of fresh- and saltwater, such as the Hudson and East Rivers that surround Manhattan. These estuaries trap the minerals that would form sand before they are able to reach the coast.
Unfortunately, erosion still occurs, and its natural forces wear away at all beachfronts over time. Because of this, it is often necessary for beaches to be supplied annually with additional sand to ensure the stability and longevity of the coastal real estate. This sand is often captured offshore.
The use of sand is not just limited to beaches, however. Since the materials that are often found in sand are quite durable, they serve many practical purposes in industry. Similar to the sand found on natural shores, according to ASTM C778-13 - Standard Specification for Standard Sand, standard sand is “silica sand, composed almost entirely of naturally rounded grains of nearly pure quartz.”
This standard sand is meant to be used only in the testing of hydraulic cements, but it and other types of sand can be used in industrial applications beyond this. Being an important component in glassmaking, metal casting, metal production, chemical production, ceramics, construction, and oil and gas recovery, the granulated mineral material is commonplace in many occupations and products. The testing method covered in ASTM D2419-14 - Standard Test Method for Sand Equivalent Value of Soils and Fine Aggregate allows for materials to be made into suitable sand for industrial purposes, while undesirable smaller or larger particles are filtered out.