Gypsum…

This entry is part 1 of 3 in the series Crystals

Calcium sulphate, commonly known as gypsum, is a soft mineral formed when calcium hydroxide (lime) reacts with sulphuric acid. It is moderately soluble but unlike most other salts it is more soluble in cold water than in hot water. Its chemical formula is CaSO4.2H2O – as it has two molecules of water associated with it in its …
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Corundum…

This entry is part 2 of 3 in the series Crystals

The hardness of minerals is measured on the Mohs Hardness Scale. Reference minerals are used with which any other mineral can be compared. The softest reference mineral is talc (from which talcum powder is produced) and the hardest is diamond. The scale compares the hardness of a given mineral by seeing the effect of scratching it …
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