igneous
Copper slag or vesicular basalt with copper minerals
Industrial slag / Basaltic matrix with secondary copper minerals
Hardness varies between 5 and 6 on the Mohs scale depending on specific mineral inclusions; color is brownish-grey with distinctive green to blue-green secondary copper staining (such as malachite or chrysocolla); luster ranges from dull to vitreous in the mineralized pockets; vesicular or glassy texture.
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Physical properties
Hardness varies between 5 and 6 on the Mohs scale depending on specific mineral inclusions; color is brownish-grey with distinctive green to blue-green secondary copper staining (such as malachite or chrysocolla); luster ranges from dull to vitreous in the mineralized pockets; vesicular or glassy texture.
Formation & geological history
Formed either as a byproduct of historical smelting operations (copper slag) or as volcanic rock (basalt/scoria) where hydrothermal solutions have deposited copper secondary minerals into vesicles over geological time.
Uses & applications
Primarily collected as mineral specimens or study pieces; historic slag is sometimes researched for industrial archaeology.
Geological facts
Copper slag is frequently mistaken for natural volcanic rocks containing native copper or copper carbonates because of its porous, vesicular nature and greenish weathering products.
Field identification & locations
Look for vesicular texture combined with bright blue-green patches or crusts; commonly found near historic mining and smelting districts worldwide.
