Our Alloys
The three 10-karat gold alloys used in Catherine Peck pieces — white, yellow, and rose — with full composition breakdowns.
Every Catherine Peck piece is made in 10-karat gold: 41.7% pure gold, alloyed with metals that give it the strength to wear daily. The remaining 58.3% varies by color — the alloy composition is what produces white, yellow, or rose, and what determines how the finished metal wears over time.
We use the same alloy specifications across every piece in a given color. This page documents those specifications in full, for anyone who wants them.
For the reasoning behind our choice of 10k, see On Gold.
10k White Gold
Alloy 0401 · RA13Our white gold is a nickel-based alloy — the hardest of the three colors we work in, and the most resistant to everyday surface wear. It finishes bright and takes rhodium plating well when a cooler, more reflective surface is desired.
Composition percentages above reflect the alloy portion only. The remaining 41.7% is fine gold. Total = 100%.
Where we use it: White gold pieces throughout the collection. Particularly well-suited to floating diamond settings where the metal should recede behind the stone, and to fancy-color stone settings where a cool base preserves color saturation.
On nickel content: This alloy contains 15.7% nickel. Individuals with confirmed nickel sensitivity should note this before ordering a white gold piece. Most people tolerate it without issue; contact us before ordering if you have known sensitivity and we can discuss alternatives.
10k Yellow Gold
Alloy 0300 · RA03A classic yellow alloy with silver in the mix — silver cools and brightens the tone slightly relative to a pure copper-zinc yellow, giving it the warmer, quieter color Catherine prefers for most yellow gold work. Harder than rose, softer than white.
Composition percentages above reflect the alloy portion only. The remaining 41.7% is fine gold. Total = 100%.
Where we use it: Yellow gold pieces throughout the collection, including most floating diamond charms and chain-based pieces. The nickel-free formula makes it the better choice for customers who prefer to avoid nickel.
10k Rose Gold
Alloy 0804 · CA15A high-copper casting alloy that produces the warm, flushed tone characteristic of rose gold. The copper content is markedly higher than in the yellow alloy — it's what drives the color. Softest of the three in raw hardness, though the casting process produces a dense, tight grain structure that wears well in finished pieces.
Composition percentages above reflect the alloy portion only. The remaining 41.7% is fine gold. Total = 100%.
Where we use it: Rose gold pieces and any design where the copper-warm tone is the intended color statement. Nickel-free.
On patina: Higher copper content means rose gold develops a patina more visibly over time than white or yellow. This is a feature of the material, not a flaw — the surface warms and deepens with wear. Pieces can be polished back to their original brightness at any time.