Iron Pyrite Aggregate is the classic "Fool's Gold". Iron Pyrite is by far the most often mineral, mistaken for real gold. The gold rush produced more fools gold that real gold. Pyrite has been mined for its sulfur content mainly. and a potential source of iron if needed. Crystal System is isometric ( square ). Hardness is 6 - 6.5. Specific Gravity is 5.1+ heavier than average minerals. Very Heavy !