Page 6 - Curriculum Visions Dynamic Book

Zinc minerals
Zinc is found among many other metals in places where rocks were once molten. Zinc makes about two-thousandths of one per cent of the Earth’s crust, making it the 25th most common element.
The most abundant and important zinc minerals are zinc sulphide (sphalerite or zinc blende) and zinc carbonate (smithsonite). Zinc sulphide is the most common of the two, occurring as dark crystals.
It is a soft, easily scratched mineral. Geologists can identify it among similar-looking minerals (such as lead compounds) by rubbing it on the surface of an unglazed tile, because it will always leave a mark with a strong brown colour. Sphalerite is found in the veins that were formed above molten igneous rocks.
 At the top of a magma chamber, hot fluids push their way into cracks and fissures in the overlying rocks. Here the liquids cool, and the minerals solidify as crystals. These places, called hydrothermal veins by geologists, are where miners look for zinc ores, especially sphalerite.
Layers of sedimentary rocks are pushed up by the rising magma.
Hydrothermal veins in which minerals are concentrated.
Rocks around the hot magma chamber are metamorphosed, or changed.
Magma from below the
Earth’s crust initially heats
the surrounding rocks but eventually cools to form granite.
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