SO, JUST WHAT IS BLACK SAND?
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I'll bet that unless you have been exposed
to gold prospecting, you have never heard of "black sand". What is it? Well, of course, it is sand that is colored black. Anyone who has been a
gold prospector or knows of someone who is, also knows that black sand
is the one thing placer prospectors are the most concerned with, other
than heavy metals such as gold.
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All throughout placer mining history, from the great Egyptians, to the
Spanish in South America and the Forty Niners, gold prospectors have had
a love hate relationship with black sand. They look for it, and once
they find it, do everything possible to remove it from the heavy metals
they know are associated with it. Some black sands separate reasonably
easily from the heavier metals, and some do not. So, if this sand is all
black sand, what is the difference?
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In case you are wondering, that's gold at
the top of the picture, and black sand trailing down from it
toward the bottom. Check out our magic panning sand on the
Gold 'N' Store page |
Placer mining, as a first step in understanding black sand, is no
mystery, but simple science. It involves specific gravity. "Specific
gravity", you say. "What is specific gravity, and what does it have to
do with black sand?" Well, they go hand in hand and one cannot be
removed from the other if you are to find gold. Specific gravity is the
wet weight relationship of everything to water, with water being zero.
Everything, once wet and under water, has a different weight than it
does in the air. This weight relationship we call specific gravity.
Placer mining depends on this relationship to separate lighter materials
from heavier ones. Black sand is one of the materials that is heavier
and in abundance, so one looks for the abundant black sand knowing that
heavier metals will also run along with it in rivers and streams. Oh,
rivers and streams are the "water" part of separating black sand from
lighter and heavier materials. Specific gravity helps us with the
separation process by classifying the different sands and gravels in
rivers and streams making it easier to find the black sand bands that
are associated with gold and other heavy metals.
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Black
sand has a specific gravity of from 5 to 11, or 5 to 11 times
the weight of water, depending on what is in the black sand.
Gold, on the other hand, has a specific gravity of around 19 and
platinum around 21. As you can see, gold and platinum can be two to three times the specific
gravity of black sand, so you now understand how you would want to find
black sand in order to find gold and other heavy metals.
"But what is in the black sand?",
you ask, and so we return to our original question, "Black Sand,
What Is It?". It contains many heavy
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materials including hematite, magnatite
(which, by the way, can be magnetic, but gets its' name from the area it
was originally found by the name of Magnesia bordering the ancient
district of Macedonia. Hematite is the
nonmagnetic one.), iron, iron pyrite, silvanites,
lead carbonates, sphalerite, chromite, and sheelite, to name the most
common, and black sand can be mildly magnetic. There are many combinations of these as well as many others in
small amounts specific to an area and too numerous to list. Suffice it
to say, they are all black or grey in color and so are known
collectively as black sand.
Finding black sand is usually essential in finding heavier minerals and
gemstones when placer mining, which are not as readily seen as black
sand. So, the next time you see that line of black sand along the
shore of a river, lake, stream or ocean, you have a better idea of what
it is..... and also what might be found along with it. Then, maybe, you
can spend time being frustrated with finding ways to separate black sand
from the more valuable minerals and gemstones often associated with it,
just like the rest of us.
Copyright 2008. All Rights Reserved Shirley Weilnau and
Hooked on Gold
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