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Calculating gold content in Quartz?


#1

Could you please supply me with formula for calculating gold content
in quartz specimens? Regards Peter


#2
   Could you please supply me with formula for calculating gold
content in quartz specimens? Regards Peter  

Peter’ You cannot calculate the gold content in a quartz specimen.
You must crush the specimen, separate the metal, melt it down and
assay it. Jerry in Ak


#3

Peter, To get an approximate calculation of the gold content in
quartz this is what you would do:

A) Figure out the volume of the quartz/gold specimen. This is
easiest done using water displacement. Or by weighing in air and
then in distilled water. (There are special scales that do this.)
Subtract one weight from the other to give you the weight of the
displaced water. Then you can find the volume of the specimen since
we all know that one gram of distilled HOH is equal to a cubic
centimeter. With this you can find the volume of the quartz/gold
specimen.

B) Obtain the actual weight of the quartz/gold specimen. A triple
beam will do.

C) Figure out what the specimen should weigh if it were pure quartz.
This is done by using the known volume of the specimen and the know
specific gravity of quartz.

D) To get the approximate weight of gold in the quartz/gold specimen
you would then subtract the above C from the above B . The difference
will give you an approximate weight of gold in the specimen.

This is only approximate since it cannot take into account any voids
(hollow areas) in the specimen, other minerals present with
different SGs, any metals alloyed with the gold, etc.

Hope that helps : ) Steve Green / Rough and Ready Gems For all
your colored gemstone BRIOLETTE needs and precision ultrasonic
drilling. See us in Tucson at the GJX Show booth # 700, Feb 6th-11th
2003 (across from the AGTA)


#4

You can make a VERY close estimate of the amount of gold in a quartz
specimen quite easily If you have a long narrow graduated lab flask
(graduated in cm), fill it half full with water Drop in the
specimen to learn the volume in cubic centimeters Weigh the piece in
grams The specific gravity of quart z is 277 That is, the specific
gravity of quartz is 277 grams per cc Multiply the volume of the
specimen x 277 and record this figure Le t’s say the volume of the
specimen is 84 cc’s 84 x 277 233 (grams) But when you weighed it,
the piece weighed 37 grams The extra weight is attributable to the
gold 37 grams - 233 grams 137 grams I f the specific gravity of
pure gold is 193, then 137 grams / 193 grams 0,71 grams of gold in
the specimen Now, if you DON’T have a graduated flask in which to the
measure the volum e of the specimen, you need to calculate the volume
using some solid geometr y methods If you have a CAD program like
Matrix (wwwgemvisioncom), and the piece is of a shape that you can
fairly closely reproduce, Matrix will calculate the volume of the
solid object for you and will calculate the weight as well, so you
don’t even need a scale! Matrix rules

Wayne Emery


#5

I think that Wayne’s formula will underestimate the amount of gold
in the specimen, as it assumes the weight of the quartz based on
total ccs of volume x specific gravity of quartz, whereas if there
is gold present, then the volume of quartz will be the total volume
of the specimen less the volume of the gold. The specific gravity of
quartz is around 2.65, with cryptocrystaline varieties sometimes
having a slightly lesser specific gravity. The specific gravity of
gold is 19.3.

Let’s use an example where the sample displaces 84ccs of water and
weighs 370 grams. If we let G be the volume of gold in the sample in
ccs, and Q be the volume of quartz in the sample in CCs, then we can
safely make the following statements;

G+Q=84
and
19.3G+2.65Q=370

We can deduce from the first statement that Q=84-G, and solve the
second statement by substitution-

19.3G+2.65(84-G)=370
19.3G+222.6-2.65G=370
16.65G+222.6=370
16.65G=147.4
G=8.85

The gold in the sample displaces 8.85ccs. The gold weighs 170.8
grams (8.85x19.3.)

Using Tv for total volume and Tw for total weight, the formula is

G=_Tw-2.65Tv_  
16.65

To obtain the weight of gold in grams, multiply G by 19.3

Of course, this is all predicated on the assumption that the sample
you have is /only/ gold and quartz. If your sample contains gold,
quartz and a third component, such as silver, this formula will not
be accurate.

Hope this helps,
Lee Einer