Could you please supply me with formula for calculating gold content

in quartz specimens? Regards Peter

# Calculating gold content in Quartz?

**jeranor**#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

**Steve_Green**#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)

**Wayne_Emery**#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

**Lee_Einer1**#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