Metal · Pt, 78, dense and white throughout
Platinum
Purer than gold as it is sold, heavier in the hand, softer at the surface and permanent in a way gold is not.
The patina question
Platinum scratches readily, and the scratches do not remove metal. They push it sideways into microscopic ridges, which collectively form the soft grey sheen called patina. Some people find this beautiful and leave it. Others have the piece polished, which takes a few minutes and removes almost nothing. Either is correct, and both are available forever, which is not true of a plated metal.
Why prongs are made of it
Even on a yellow gold ring, a good jeweller will frequently make the prongs from platinum. It is more ductile, holds a bent shape without springing back, and resists the gradual thinning that causes prong failure. A platinum prong on a gold setting is a sign of a jeweller thinking about the thirty year horizon rather than the invoice.
The price relationship, which moves
Platinum has traded both above and below gold within the last two decades, which surprises people who assume a fixed hierarchy. The market for platinum is driven heavily by industrial demand, particularly catalytic converters, so its price moves with the car industry in a way gold does not. When comparing a platinum and a white gold setting, ask for both quotes rather than assuming the premium, because it varies more than the trade lets on.
Platinum against 18 carat gold
The comparison that matters when choosing a setting for a stone you intend to keep.
How to check it
- Look for the mark: 950, PLAT, or PT950 inside the band.
- Weight is the giveaway. A platinum ring next to an identical white gold one is unmistakably heavier.
- Colour under daylight. White gold has a faint warm or bluish cast from the rhodium. Platinum is a slightly grey, even white.
- Ask what the prongs are made of, even on a gold ring. The answer tells you about the jeweller.
Care
- Clean as for gold, warm water and a soft brush.
- Decide whether you want the patina or the polish, and tell the jeweller. They will polish by default.
- Platinum does not tarnish or oxidise, so there is nothing to prevent, only dirt to remove.
- Resizing is possible but more difficult than gold, so buy the size properly the first time.