Minerals

Clues in this puzzle

Across

• Heavy metallic element found bound in hematite and magnetite (4)
• Volcanic glass that fractures with razor-sharp conchoidal edges (8)
• Major zinc ore whose high dispersion yields exceptional gemstone fire (10)
• Borosilicate gem famous for multicolored watermelon color zoning (10)
• Combustible sedimentary rock formed from ancient compressed plant matter (4)

Down

• Corundum variety that blushes deep red thanks to chromium (4)
• Amorphous hydrated silica displaying a vivid internal play of color (4)
• Toxic bright red mercury sulfide ore used to produce vermilion (8)
• Opaque, microcrystalline quartz variety known for earthy reddish tones (6)
• Precious yellow metal that does not tarnish or rust over millennia (4)
• Benchmark for the lowest rank on Mohs scale (4)
• Metallic component extracted primarily from the ore sphalerite (4)

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