Why 18 Carat Gold Is the Jeweller's Preferred Standard

Eighteen-carat gold is exactly 75% pure gold. The remaining 25% is not an impurity; it is a carefully measured blend of copper, silver and zinc. In Italy, this proportion has been the standard for fine jewellery for so long that the 750 hallmark functions as a badge of reliability. Yet the unalloyed 24-carat metal is rarely used for pieces intended to be worn daily. Pure gold is too soft to hold a claw or seat a stone securely.

The Metallurgy Behind the Mark

Gold atoms slide over one another with remarkable ease, which is why a 24-carat band can scratch and distort within weeks. Adding 25% alloying metals changes the crystal structure, giving 18-carat gold enough hardness for everyday wear while retaining its warm tone. Copper brings a blush, silver softens the hue, and zinc acts as a deoxidiser during casting. The precise recipe can be adjusted to produce rose, yellow or white gold without altering the 750 parts per thousand of gold. This is metallurgy as subtle as any stone-cutting, and it decides whether a ring survives a lifetime of hand-washing.

Why the Alloy Matters

At 18 carat, a setting is strong enough to hold a diamond or emerald in place but still supple enough for a jeweller to shape by hand. A higher gold content, such as 22 carat, is luminous but prone to bending; a lower one, such as 14 carat, is harder but can look pale and dull against warmer skin tones. Italian jewellers therefore choose 18 carat as the balance between beauty and utility. The alloy also polishes to a deeper mirror finish than lower-gold alloys, revealing the sharp facets and crisp edges of granulation and filigree work. When you inspect a piece, look at the edge of a shank or the back of a clasp—that quiet gleam is the signature of a well-mixed alloy.

A Hallmark Worth Seeking

In Italy, the mark for 18-carat gold is 750, meaning 750 parts per thousand. A maker's punch and, in many cases, a small identity number sit beside it, allowing the piece to be traced back to its workshop. These marks are tiny, often hidden inside a band or behind a pendant setting, and they are the closest thing this industry has to a signature. Look for the numbers if you want to be sure: they may be laser-stamped, but they are always there. At Gioielleria Patricia Oro, every 18-carat piece is selected with that mark in mind, because a hallmark is not bureaucracy; it is proof of intention.