What is the plural of platinum?

In the card game Dominion, I always thought that the “Platinum” card, in the plural form, would be “Platinums”. However, Dominion Online lists the plural form as “Platina”.

Is this correct, or is Dominion Online wrong?

According to The Cambridge Dictionary the plural form is the same as the singular one:

platinum noun (no plural )

a silver-coloured metal that is very valuable

Plata is the Spanish form from which platinum derives:

Origin of platinum

Modern Latin from Spanish platina, diminutive of plata, silver from Prov, metal plate, silver bar, silver from Vulgar Latin an unverified form plattus, flat.

(Yourdictionary.com)

The plural form for the game is “platinum cards”:

Platinum is a basic Treasure card from Prosperity. It and Colony may be added to the supply in games using Kingdom cards from Prosperity. The Platinum pile contains 12 cards.