When you tell this to people they often laugh at you.
You get remarks like: “I have a sandbox for you in the garden” or “can you use the sand of my birdcage too?”
In volcanic areas you often find black sands, for example near Naples (Italy), The Canary Islands, Iceland or Hawaii.
White beach sand can exist of calcium grains of worn out coral reeves and shells.
Other examples of colors in sand are: red iron containing sands in many deserts, white gypsum sand in White Sand in
New Mexico, green sand and there even is a blue-lilac sand.
Sand with olivine from Hawaii – Papakolea beach
A world opens when you study sand grains.
When Dutch people hear the word SAND, they think of the yellow beach and dune sand of our coasts.
This sand exists of little round grains of less than 1 mm in diameter, which exist of a transparent, glassy,
hard material: quartz.
When you look closer there are many more kinds of sand.
Besides the round sea sands there are also angular river sands, sands from mountain slopes, sands of glaciers and
round dull desert sands.
The origin of the sand defines the color and the composition.
There is more to sand than only the color.
Sand is for a geologist an aid to get an idea about the rocks which occur in the area of origin, about the erosion of the
sand and about the circumstances under which this sediment eventually was deposed.
Of course all of this information gives interesting knowledge to the amateur geologist.
For sure he can learn from the professional, what to look for in the material that was found.
Sand from Ameland with heavy materials: white=quartz, black=magnetite or ilmenite,
pink=garnet, yellow=epidote, orange=staurolite, dull-brown=leukoxeen.
So far we only talked about the minerals in the sand.
You also can find little fossils in it, like the stings of sea urchins, little bryozoans and brachiopods, tiny but wonderful
foraminifera.
Sand is transported not only by running water, but also through the wind.
This is demonstrated by the dunes along the coast and the barchans in the desert.
Desert sand is often dull and very rounded by the sanding of the grains against each other under the influence of the
wind.
River sand on the other hand is usually angular. This makes it suited for the sand sculptures on the beach.
Collecting sand – a boundless hobby
There is more in sand than you think.
Sand collectors, who collect sand from all over the world, possess a great palette of colors of sand samples, stored in
little boxes, bags or little glass bottles.
When you take a good look under a microscope than you can see how beautiful sand really is.
Erosion: smaller and rounder
At the beginning of the journey from area of origin to deposit site – say from Alp glacier to Scheveningen – there is
weathering of the hard rock and erosion.
The cracked and into pieces broken rubble is transported through gravity: rocks roll down from a slope.
In a valley, in the range of a river, running water get a grip on it.
The greater force of the water, the larger are the rocks that can be moved, but through sanding and clashing the
pieces will be increasingly crushed.
Fast running rivers often have a bed of gravel.
Eventually, downstream, there will be only clay and sand on the bed of the river.
Once arrived in the sea, the tidal flows and the surfs will take care of the further transport of the grains.
Reduction and sorting of the grains – now we call it sand – that falls within the size of 0,05 – 2 mm, happens in the surf
zone.
Look at the surf
In the sea lie mixed the degradation products of the outback, the composition depends of the rocks which occur in the
outback.
In case of the Rhine there are both magmatic, metamorphic as sedimentary rocks, which mostly contain quartz.
Some rock-forming minerals are not resistant, for instance biotite.
The result is a sand that for the main part is formed by quartz grains.
When you look at it close you can see here and there a dark grain.
But there are places where the dark and heavy minerals are highly concentrated.
In this case the sea seems a perfect mechanic and with the help of the sea breeze the sea sorts the grains in the surf
zone with precision to size and weight.
Because of this process you can find on the beach clearly visible dark zones of heavy minerals.
For instance you can see that the moreover light beach sand has a pink color, with here and there black strings.
How come? The ascending waves of the surf brought pink garnet grains and black ilmenite and magnetite to the beach,
during storms even very high and the descending water movement could remove the coarse quartz grains, but not all
of the finer heavy mineral grains.
The heavy minerals stayed behind and concentrations of them were the result.
Concentrations of heavy sand are found at the Dutch coast, among other near Petten, Kijkduin and Ameland.
Except garnet and the black ore mineral ilmenite and magnetite in the dark sand of Ameland you can find about 20
different other minerals, like: tourmaline, epidote, titanite, staurolite, rutile, leucoxene, disthene, spinel, augite and
zircon.
Not all of them are dark, but they are heavy.