Sand is a naturally occurring granular material composed of finely
divided rock and mineral particles. It is defined by size, being finer
than gravel and coarser than silt.
Sand can also refer to a textural
class of soil or soil type; i.e., a soil containing more than 85
percent sand-sized particles by mass.
The composition of sand varies, depending on the local rock sources
and conditions, but 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. The second
most common type of sand is calcium carbonate, for example, aragonite,
which has mostly been created, over the past half billion years, by
various forms of life, like coral and shellfish. For example, it is
the primary form of sand apparent in areas where reefs have dominated
the ecosystem for millions of years like the Caribbean.
Sand is a non-renewable resource over human timescales, and sand
suitable for making concrete is in high demand.
4 Resources and environmental concerns
6 See also
8 External links
Heavy minerals (dark) in a quartz beach sand (Chennai, India).
Sand Dunes State Park, Utah. These are grains of
quartz with a hematite coating providing the orange color.
Sand from Pismo Beach, California. Components are primarily quartz,
chert, igneous rock and shell fragments.
The exact definition of sand varies. The scientific Unified Soil
Classification System used in engineering and geology corresponds to
US Standard Sieves, and defines sand as particles with a diameter
of between 0.074 and 4.75 millimeters. By another definition, in terms
of particle size as used by geologists, sand particles range in
diameter from 0.0625 mm (or 1⁄16 mm) to 2 mm. An
individual particle in this range size is termed a sand grain. Sand
grains are between gravel (with particles ranging from 2 mm up to
64 mm by the latter system, and from 4.75 mm up to
75 mm in the former) and silt (particles smaller than
0.0625 mm down to 0.004 mm). The size specification between
sand and gravel has remained constant for more than a century, but
particle diameters as small as 0.02 mm were considered sand under
Albert Atterberg standard in use during the early 20th century. A
1953 engineering standard published by the American Association of
State Highway and Transportation Officials set the minimum sand size
at 0.074 mm. A 1938 specification of the United States Department
Agriculture was 0.05 mm.
Sand feels gritty when rubbed
between the fingers. Silt, by comparison, feels like flour).
ISO 14688 grades sands as fine, medium, and coarse with ranges
0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the
United States, sand is commonly divided into five sub-categories based
on size: very fine sand (1⁄16 – 1⁄8 mm diameter),
fine sand (1⁄8 mm – 1⁄4 mm), medium sand
(1⁄4 mm – 1⁄2 mm), coarse sand (1⁄2 mm
– 1 mm), and very coarse sand (1 mm – 2 mm). These
sizes are based on the Krumbein phi scale, where size in Φ = -log2D;
D being the particle size in mm. On this scale, for sand the value of
Φ varies from −1 to +4, with the divisions between sub-categories
at whole numbers.
Close up of black volcanic sand from Perissa, Santorini, Greece
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.
The composition of mineral sand is highly variable, depending on the
local rock sources and conditions. The bright white sands found in
tropical and subtropical coastal settings are eroded limestone and may
contain coral and shell fragments in addition to other organic or
organically derived fragmental material, suggesting sand formation
depends on living organisms, too. The gypsum sand dunes of the
White Sands National Monument
White Sands National Monument in
New Mexico are famous for their
bright, white color.
Arkose is a sand or sandstone with considerable
feldspar content, derived from weathering and erosion of a (usually
nearby) granitic rock outcrop. Some sands contain magnetite, chlorite,
glauconite or gypsum. Sands rich in magnetite are dark to black in
color, as are sands derived from volcanic basalts and obsidian.
Chlorite-glauconite bearing sands are typically green in color, as are
sands derived from basaltic (lava) with a high olivine content. Many
sands, especially those found extensively in Southern Europe, have
iron impurities within the quartz crystals of the sand, giving a deep
Sand deposits in some areas contain garnets and other
resistant minerals, including some small gemstones.
An electron micrograph showing grains of sand
Pitted sand grains from the Western Desert, Egypt. Pitting is a
consequence of wind transportation.
The study of individual grains can reveal much historical information
as to the origin and kind of transport of the grain.
that is recently weathered from granite or gneiss quartz crystals will
be angular. It is called grus in geology or sharp sand in the building
trade where it is preferred for concrete, and in gardening where it is
used as a soil amendment to loosen clay soils.
Sand that is
transported long distances by water or wind will be rounded, with
characteristic abrasion patterns on the grain surface. Desert sand is
People who collect sand as a hobby are known as arenophiles. Organisms
that thrive in sandy environments are psammophiles.
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Sand sorting tower at a gravel pit.
Agriculture: Sandy soils are ideal for crops such as watermelons,
peaches and peanuts, and their excellent drainage characteristics make
them suitable for intensive dairy farming.
Sand makes a low cost aquarium base material which some
believe is better than gravel for home use. It is also a necessity for
saltwater reef tanks, which emulate environments composed largely of
aragonite sand broken down from coral and shellfish.
Geotextile bagged sand can serve as the foundation
for new reefs.
Artificial islands in the Persian Gulf.
Beach nourishment: Governments move sand to beaches where tides,
storms or deliberate changes to the shoreline erode the original
Brick: Manufacturing plants add sand to a mixture of clay and other
materials for manufacturing bricks.
Cob: Coarse sand makes up as much as 75% of cob.
Sand is often a principal component of this critical
Sand rich in silica is the principal component in common
Hydraulic fracturing: A drilling technique for natural gas, which uses
rounded silica sand as a "proppant", a material to hold open cracks
that are caused by the hydraulic fracturing process.
Sand makes small hills and slopes (golf courses would be
Sand is mixed with masonry cement or Portland cement and lime
to be used in masonry construction.
Paint: Mixing sand with paint produces a textured finish for walls and
ceilings or non-slip floor surfaces.
Railroads: Engine drivers and rail transit operators use sand to
improve the traction of wheels on the rails.
Recreation. Playing with sand is a favorite beach time activity. One
of the most beloved uses of sand is to make sometimes intricate,
sometimes simple structures known as sand castles. Such structures are
well known for their impermanence.
Sand is also used in children's
Special play areas enclosing a significant area of sand, known
as sandboxes, are common on many public playgrounds, and even at some
single family homes.
Sand improves traction (and thus traffic safety) in icy or
Sand animation: Performance artists draw images in sand. Makers of
animated films use the same term to describe their use of sand on
frontlit or backlit glass.
Sand casting: Casters moisten or oil molding sand, also known as
foundry sand and then shape it into molds into which they pour molten
material. This type of sand must be able to withstand high
temperatures and pressure, allow gases to escape, have a uniform,
small grain size and be non-reactive with metals.
Sand castles: Shaping sand into castles or other miniature buildings
is a popular beach activity.
Sandbags: These protect against floods and gunfire. The inexpensive
bags are easy to transport when empty, and unskilled volunteers can
quickly fill them with local sand in emergencies.
Sandblasting: Graded sand serves as an abrasive in cleaning,
preparing, and polishing.
Thermal weapon: While not in widespread use anymore, sand used to be
heated and poured on invading troops in the classical and medieval
Water filtration: Media filters use sand for filtering water.
Wuḍūʾ: the Islamic procedure for washing parts of the body.
Zoanthid "skeletons": Animals in this order of marine benthic
cnidarians related to corals and sea anemones, incorporate sand into
their mesoglea for structural strength, which they need because they
lack a true skeleton.
Resources and environmental concerns
Only some sands are suitable for the construction industry, for
example for making concrete. Because of the growth of population and
of cities and the consequent construction activity there is a huge
demand for these special kinds of sand, and natural sources are
running low. In 2012 French director
Denis Delestrac made a
documentary called "
Sand Wars" about the impact of the lack of
construction sand. It shows the ecological and economic effects of
both legal and illegal trade in construction sand.
Sand's many uses require a significant dredging industry, raising
environmental concerns over fish depletion, landslides, and
flooding. Countries such as China, Indonesia, Malaysia and
Cambodia ban sand exports, citing these issues as a major factor.
It is estimated that the annual consumption of sand and gravel is 40
billion tons and sand is a US$70 billion global industry.
While sand is generally non-toxic, sand-using activities such as
sandblasting require precautions. Bags of silica sand used for
sandblasting now carry labels warning the user to wear respiratory
protection to avoid breathing the resulting fine silica dust. Safety
data sheets for silica sand state that "excessive inhalation of
crystalline silica is a serious health concern".
In areas of high pore water pressure, sand and salt water can form
quicksand, which is a colloid hydrogel that behaves like a liquid.
Quicksand produces a considerable barrier to escape for creatures
caught within, who often die from exposure (not from submersion) as a
Wikiquote has quotations related to: Sand
Desert sand (color)
Energetically modified cement
Energetically modified cement (EMC)
Heavy mineral sands ore deposits
White Sands National Monument
^ Glossary of terms in soil science (PDF). Ottawa:
1976. p. 35. ISBN 0662015339.
^ Constable, Harriet (3 September 2017). "How the demand for sand is
killing rivers". BBC News Magazine. Retrieved 9 September 2017.
Soil Classification System
^ Urquhart, Leonard Church, "Civil Engineering Handbook" McGraw-Hill
Book Company (1959) p. 8-2
^ Seaweed also plays a role in the formation of sand. Susanscott.net
(1 March 2002). Retrieved on 24 November 2011.
^ Krinsley, D.H., Smalley, I.J. 1972. Sand. American Scientist 60,
^ "Psammophile". Merriam-Webster.com. Retrieved 27 January 2016.
^ "Importing Sand,
Help Restore Beaches". NPR.org. 17 July
Sand Wars teaser here.
Simon Ings (26 April 2014). "The story of climate change gets star
treatment". New Scientist: 28–9.
^ Strände in Gefahr? Arte Future, last updated 23 April 2014
^ Torres, Aurora; et al. (8 September 2017). "The world is facing a
global sand crisis". The Conversation. Retrieved 9 September
2017. CS1 maint: Explicit use of et al. (link)
^ "The hourglass effect". The Economist. 8 October 2009. Retrieved 14
^ Beiser, Vince (26 March 2015). "The Deadly Global War for Sand".
Wired. Retrieved 26 March 2015.
Silica sand MSDS. Simplot (13 March 2011). Retrieved on 24 November
Look up sand in Wiktionary, the free dictionary.
Media related to
Sand at Wikimedia Commons
Beach Sand: What It Is, Where It Comes From and How It Gets Here -
Beaufort County Library
Beach, Chandler B., ed. (1914). "Sand". The New Student's
Reference Work. Chicago: F. E. Compton and Co.
Sand Mining Side Effects
The World Is Running Out Of
Sand - New York Times
Sand Mining In India Rivers Causing Problems - New York Times
How Demand For
Sand Is Killing Rivers In Africa - BBC
Sand - BBC
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