Key Ideas about Sand
- Sand comes from rocks or skeletons of plants and animals that
are broken down into very small particles by wind and waves. Sand
made from skeletal material of plants and animals (Biogenic
Sand) is made of calcium carbonate. Sands made from rocks
(Mineral Sand) are made of silica, basalt, or other minerals
and are primarily derived from volcanoes.
- The colour of a sandy beach comes from the most common minerals
or skeletal materials. On the east coast of New Zealand, sands
have lots of quartz and feldspar mineral content and are light
coloured pink, brown or white. The sand on Coromandel beaches
is very white and if you look closely the sand grains are almost
- The sand on the west coast also contains black particles of
basalt from old lava flows and is darker in colour.
- The size of the sand particles depends on their exposure to
the surf. Coarse sand, made up of large sand particles, are near
the surf and the smaller grains are up in the dunes. The different
sizes of sand grains result from the different ages of the particles
and their hardness.
- Sand moves easily, almost like a liquid. This makes it a very
difficult habitat to live in and creatures, like the Toheroa,
need special adaptations to survive in it. Plants
that grow on the upper reaches of the beach also need special
adaptations to survive.
- Sand moves up the beach to the sand dunes during fine weather
and is washed back into the sea during storms. This cycle is important
in protecting areas behind the sand dunes (where there may be
- Sand also moves along the beach with each wave. If there is
a storm from an unusual direction, the beach might be changed
dramatically from one day to the next.
- Any hard rock or other structure put in the path of the moving
sand creates a disturbance in the flow and results in changes
in the look of the beach.
- Most beaches have a hard, sand-stone base. Sand-stone is made
as fresh ground water seeps through the sand and cements the particles
- White quartz sand is made of silica, which is mined to make
glass. Black sand is often mined for iron to make steel. But the
greatest amount of sand mining is to supply sand for cement. All
cement contains sand, and almost all modern buildings use lots