Spanish Pyrite (1)

Single Pyrite cube on Matrix.

Isn’t it amazing that this formation is aaall natural!?

These Pyrites from Spain are only able to be mined with certain permissions, and not all year round. 
Pyrite, or iron pyrite is an iron sulphide. This mineral's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of "Fool's Gold."