GARY RETHERFORD / SCIENCE PHOTO LIBRARY GARY RETHERFORD / SCIENCE PHOTO LIBRARY
Macrophotograph of sulphur crystals. Sulphur is frequently arranged in fine, dipyramidal crystals, granular aggregates, impregnations and incrusta- tions. Colour varies from the characteristic yellow lemon, when the mineral is pure, to brown and black. It is a soft, very light and fragile mineral. It fuses at very low temperature (119 Celsius) and burns at 275 Celsius giving off toxic sulphur dioxide fumes. It is associated with sedimentary deposits of the evaporite type and with oil-bearing deposits. Most commercial sulphur derives as a by-product of the oil industry and is the raw material used in the manufacture of sulphuric acid.
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