set: minerals // series: // picture: 1
Many minerals form at elevated temperatures and pressures at depth in the Earths crust. Subsequent uplift and erosion may expose them to the influences of the Earths atmosphere and then they may no longer be stable. This is a sample of the mineral goethite (FeO.OH), a common surface alteration product of iron-bearing sulphides such as pyrite. The recognition of this weathered material (known as iron hat or gossan) is important in mineral exploration as it often indicates the presence of unweathered ore minerals at greater depths.
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