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What is sand? It is mineral material consisting of particles ranging in size from 1/16 mm to 2.0 mm.
Sand, gravel, silt and clay are known as sediment: they are produced by the breakdown of
rocks, either mechanical or chemical. Sand is a granular material, a conglomeration of discrete solid,
macroscopic particles characterized by a loss of energy whenever the particles interact (friction when
grains collide). When a piece of rock breaks down, it erodes further and is carried
away from its source by wind, water or ice. Eroding, the material becomes easier to transport.
When it becomes smaller than 2.0 mm, we speak of ‘sand’.
Location
Sand usually lies on beaches and the bottom of the sea, but may be found in other placed too, such as rivers,
lakes, caves and hillsides. Large quantities of sand can be found in the desert. One fifth of the earth surface
consists of deserts, however, note that not every desert consists of sand.
Composition
Roughly, sand is a mixture of three kinds of materials;
1. Detrital fragments, meaning small fragments of rock and minerals
The most common mineral in sand (especially in inland continental settings and non-tropical coastal settings)
is quartz. Kinds of rock that you may find are feldspar, mica, calcite and gypsum, depending on the
geological origin, and volcanic debris (basalt, pumice). Some of the components of sand are magnetic (iron,
magnetite), others contain gold and precious gems.
2. Biogenic particles, such as shells or parts of shells
In sand, you’ll also find the remains of animals and plants. Mostly shells, but coral fragments and skeletons
of plankton too. Most of these biogenic particles are made out of calcium carbonate, just like most
3. Chemical precipitates, like evaporites and oolites
Evaporites form when sea water evaporates; atoms such as calcium, sodium and chlorine are left behind
and form solid rocks. Oolite is a type of sedimentary rock which is a mixture of ooids, a type of sand
That usually form on the seafloor, and other sedimentary materials.
Texture
Defining the texture of sand, important parameters are size, rounding and sorting.
1. Size
As said before, sand consists of particles ranging in size from 1/16 mm to 2.0 mm. This can be sub-divided
into five catagories;
Very coarse 1.0 - 2.0 mm
Coarse 0.5 - 1.0 mm
Medium 0.25 - 0.5 mm
Fine 0.125 - 0.25 mm
Very fine 0.0625 - 0.125 mm
Everything larger than 2.0 mm is called gravel. Material with particles smaller than 0.0625 mm is either
silt or clay; these particles are too small to see with the eye. Sand gets smaller the further it gets transported,
this means that large grains of sand are likely to have travelled only a small distance.
2. Rounding
Erosion that accures during transport also makes the grains rounded; A well rounded grain of sand is likely
to have travelled far. But it might also be that the durability of the material isn’t very high.
3. Sorting
A well-sorted sample of sand contains grains that are all about the same size. If a sample contains particles
which are smaller or larger than sand (silt or gravel), it is poorly sorted. This depends on the distance of
transport, as well as the way it is transported. Wind only transports the finest sand, therefore it sorts very
well. Ice transports all sizes of material, from clay to large stones, therefore it does not sort at all.
Uses of sand
Sand is a principal component of the aggregate used in the preparation of concrete. Sand manufactured at
rock crusher plants for use as an aggregate is called mansand. Graded sand is used as an abrasive in
sandblasting and is also used for filtering water. Sandy soils are ideal for certain crops, such as watermelons
and peanuts, and are often preferred for intensive dairy farming. This is because of their excellent drainage
characteristics. Sand bags are used for protection against floods and gun fire. And of course,children love
to play with sand on the beach or in a sandbox.
Hazards of sand
When working with sand often, it is dangerous to breath the fine silica dust that contains it.There have been
a number of lawsuits in recent years where workers have sought damages after they developed silicosis,
which is a lung disease caused by inhalation of these fine silica particles. Some people have been severely
injured and even killed after digging sand "caves" in large dunes or sandhills when the cave collapsed upon
them.
Trivia
*To pick up sand grains, the air has to be moving at least 15 miles/24 km per hour.
*In beachsand, the grains of sand make up 55 to 60% of the total volume. In quicksand, on the other
hand, this percentage is about 40% You could drown in it, just like in water.
Spotted any mistakes or typo’s in this text? Have any information to add? Let me know!
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