Carat Fineness Precious Metals

Overview

Engineering reference data for Carat Fineness Precious Metals in material science and properties.

Key Formulas

Stress

$\sigma = \frac{F}{A}$

Force per unit area.

Strain

$\varepsilon = \frac{\Delta L}{L_0}$

Change in length per original length.

Hooke's Law

$\sigma = E \varepsilon$

Stress proportional to strain in elastic region.

Thermal Expansion

$\Delta L = \alpha L_0 \Delta T$

Length change due to temperature.

Variables

Definitions

Fineness is the proportion of pure precious metal in an alloy, expressed in parts per thousand (‰, also written as "o/oo"). Karat (K or kt) is a unit of measurement for the purity of gold alloys, where pure gold is defined as 24 karat.

Karat and Fineness Formula

The purity of gold can be calculated from its karat rating using the following formula:

$$\text{Fineness (decimal)} = \frac{\text{Karat}}{24}$$

To express this as a percentage or in parts per thousand (‰), the conversion is:

$$\text{Fineness (\%)} = \left( \frac{\text{Karat}}{24} \right) \times 100$$ $$\text{Fineness (\permil)} = \left( \frac{\text{Karat}}{24} \right) \times 1000$$

Gold Alloy Properties and Common Karat Ratings

The following table summarizes common karat ratings, their equivalent fineness, and their typical suitability for jewelry applications. Pure gold (24 K) is very soft and is almost always alloyed with other metals like silver, copper, nickel, or zinc to improve its strength and durability.

Permille Notation in Gold Fineness

Gold fineness is often expressed in parts per thousand (permille), denoted as o/oo. The conversion from karat to permille is given by:

$\text{Permille} = \left( \frac{\text{Karat}}{24} \right) \times 1000$

Below is a reference table for common karat values and their equivalents in fraction, percentage, and permille:

References

• Original Source