# Basic metallurgy for jewelers: how metal behaves

> Precious and base metal, alloy, fineness, karats, hardness, malleability, melting point, cold working and annealing: a jeweler's basic metallurgy.

- Source: https://www.711grados.com/en/basic-metallurgy-for-jewelers/
- Language: en
- Note: This entry was drafted with the help of AI and is pending review by the author.
- Published: 2026-05-27
- Updated: 2026-05-27
- Translation (es): https://www.711grados.com/es/metalurgia-basica-para-joyeros/
- Author: Sandra Sánchez
- Site: 711 Grados (https://www.711grados.com/)

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Understanding how metal behaves explains why it cracks, why it needs annealing or why a piece changes size when cast. These are the key ideas.

## Kinds of metal

- **Precious metal (metal precioso):** gold, silver, platinum and palladium, among others. They are scarce and resist corrosion.
- **Base metal (metal base):** copper, brass, bronze, steel, aluminum… They are cheaper and some of them tarnish.
- **Alloy (aleación):** a mix of metals to change hardness, color or melting point. See [jewelry alloys](https://www.711grados.com/en/jewelry-alloys-how-they-are-made/).

## Purity

- **Fineness (ley):** the proportion of pure metal, in thousandths. Sterling 925 means 925 parts silver in every 1000. See [925 silver](https://www.711grados.com/en/what-is-925-silver/).
- **Karat (quilataje):** the purity of gold in 24 parts. 18-karat gold is 18/24 gold, that is, 750 thousandths. It is not the same as the carat of gems: see [carat and karat](https://www.711grados.com/en/carat-of-gems-and-karats-of-gold/).
- **Purity (pureza):** the general term for pure-metal content.

## Mechanical properties

- **Hardness (dureza):** resistance to scratching or deformation. It is not the same as the Mohs hardness of gems.
- **Malleability (maleabilidad):** the ability to be flattened into sheet without breaking. Gold and silver are very malleable.
- **Ductility (ductilidad):** the ability to be drawn into wire. It is the basis of [wire drawing](https://www.711grados.com/en/rolling-and-wire-drawing/).

## Heat

- **Melting point (punto de fusión):** pure gold melts at about 1064 °C, pure silver at about 962 °C, copper at about 1085 °C and platinum at about 1768 °C.
- **Melting temperature of an alloy:** not a single point but a range between the start (solidus) and the end (liquidus) of melting.
- **Shrinkage (contracción):** metal shrinks as it cools, which is allowed for when casting.

## Changes when you work metal

- **Cold working (trabajo en frío):** hammering, rolling, bending or drawing at room temperature. It hardens the metal and makes it brittle. Also called *work hardening*.
- **Internal stress (tensión del metal):** stress built up by working it; it can warp or crack the piece later.
- **Annealing (recocido):** heating the metal to remove hardness and stress and recover malleability. See [annealing](https://www.711grados.com/en/annealing-metal/).
- **Hot working (trabajo en caliente):** forging and other processes at high temperature, where the metal is softer.
- **Oxidation (oxidación):** a reaction with oxygen; on copper and sterling silver it forms dark oxides. See [pickling](https://www.711grados.com/en/pickling-metal/).

## The practical rule

Work the metal until you feel it push back, **anneal** it and carry on. Ignoring this is the most common cause of cracks.

See also: [Basic metalworking operations](https://www.711grados.com/en/basic-metalworking-operations/).