__How to Estimate Gold Content in Gold Plated Parts__

When trading electronic scrap or jewelry, we sometimes have to quote plated materials.

When the material is homogenic, we can estimate the gold content in **3 main ways**:

- The most accurate way is taking a sample, dissolving the gold in a solution, precipitating it and

then casting the precipitated gold. This is actually a refining process (which is more complicated and

not suitable for everyone). You can learn more in this video.

- In case the plated materials are brass or copper it is possible to cast a sample and analyze it with “Fire Assay” or XRF to identify the gold content.

- A
**less accurate but quick method**, is estimation of gold content by the thickness of the gold-plated parts. This method is limited in its accuracy due to non-homogenous coating layer, and the

difficulty in estimating surface area. **However**, it can enable getting an idea about gold content by

__using following formula__: **X = ( ^{1000}/_{W}) x S x T x 19.3**

X = Total gold in gram / per Kg scrap

W = Part weight in grams

T = Thickness of plated material in cm (XRF test)

S = Estimated surface area of the part in cm²

Ƥ = Gold density 19.3 g/cm² (constant)

__Example #1:__

We have a ball with a diameter of 0.5 cm, weight of 0.6 g and thickness of 2 µm.

We calculate:

S = π D² = 3.14 x 0.5² = 0.785 cm²

T = 2 µm = 0.0002 cm

W = 0.6 g

X = Total gold in gram per 1 Kg Scrap = (^{1000}/_{0.6}) x 0.785 x 0.0002 x 19.3 = **5.05 gr/Kg**

Gold plated thickness can be analyzed with XRF (some XRF does not have this application).

For your convenience, please use our Gold plated parts Calculator

* Note: 1 µm = 0.0001 cm

**Example: # 2** (according to the below picture)

In order to estimate those “windows parts” made of brass, gold plated (with Nickel coating layer preliminary to the gold, as a block layer, so the gold will not diffuse into the brass over the time).

First we have to identify parts weight & gold layer thickness.

Three important parameters –

** Calculating the surface area** – (in this case, it is relatively easy as the parts are symmetric and easy to measure) according to our calculation, the surface area is 3.6 square centimeter.

** The weight of each piece** – we weighed 10 pieces, then divided to 10, in order to get an average (as not all parts have the same weight) – we have received, 1 Pcs. weight is 1.87 gram.

** Thickness of the plated laye**r – we use the “Fischerscope X-Ray XDL 23” (or similar device) – we took 12 different measurements, of few parts (at different spots on the parts) an average thickness measurement was 0.528-micron meter.

1 micrometer is equal 0.0001cm so, measurement result is 0.0000528 Centimeter.

Now let’s calculate how much gold we have in 1Kg of those

“Gold plated items” –

Total surface area per 1 kg parts = 3.6 X 1,000/1.87=1,925 square cm.

(1,000 / 1.87 is the number of parts in 1 Kg.)

The formula for calculating the gold content in 1Kg parts:

(surface area) x (coating thickness) x (gold density) = Gold (gr/Kg)

1,925 x 0.0000528 x 19.3 = 1.96 gr/Kg

Density of gold is 19.3 cubic cm.

We can estimate that these parts contain 1.96 gram of gold per 1 Kg. of plated parts.

The photo below shows the same results, when using our calculator.

A.G. Metals is a leader in the field of precious metals, with over two and a half decades of experience specializing in the trading & recycling of precious metals.

__ __

__Ami Gur__

__A.G. Metals Ltd.__

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