Metal Set Precious Metals
Type Ore
Mineable Level: 3
Experience Rewarded 20
Tool Stats
Durability 100
Mining Level 3
Enchantability 50
Spawn info
Veins per Chunk 3
Ore per Vein 3

It's an ore in Precious Metals. It is used in the crafting of armor, tools, swords and platinum chest.

Platinum is also used in mix with other metals to make Alloys:

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Platinum armor, blocks, and tools.