JEREMY BISHOP / SCIENCE PHOTO LIBRARY JEREMY BISHOP / SCIENCE PHOTO LIBRARY
Crystals of haematite in quartz. Hematite (black, centre) is a variety of iron oxide (Fe2O3), mined as one of the main ores of iron. The specimen shown here has a bulbous appearance, also referred to as botryoidal (grape-like). It is a small specimen, less than a millimetre across. The surrounding mineral (white) is quartz, a form of silica (silicon dioxide, SiO2). This specimen is from St Just, Cornwall, England.
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