Page 8 - Curriculum Visions Dynamic Book

Gemstones containing aluminium
Whereas clay is made of tiny, unremarkable crystal plates that are too small to
see without a powerful microscope,
just occasionally, usually near
where volcanoes have been active, aluminium combines with other elements to form some of the world’s most remarkable crystals. These are gemstones such as sapphire and ruby.
Ruby
Ruby is a deep red crystal, one of the most prized of all gemstones. It is made mainly of aluminium and oxygen (aluminium oxide). This mineral, known as corundum, is transparent. But when it occurs with small amounts of another element, chromium, the colour changes to somewhere between pale rose and
deep red.
The world’s best rubies come from
Myanmar (Burma), where they have been naturally weathered from rocks and washed by rivers to accumulate among river gravels.
Small rubies can now be made artificially, and these are routinely used in many of the world’s lasers.
 Beryl is made from aluminium, beryllium, silicon and oxygen.
In its pure form it makes emerald, a deep green transparent gemstone, and a paler version called aquamarine.
Beryl forms six-sided crystals, making the mineral crystals easy to identify. It is often found associated with volcanic rocks.
Emeralds are found where volcanic activity has altered limestones, often in the form
of very large crystals. One of the largest crystals found weighed 200 tonnes! Needless to say, this was not of the transparent gemstone variety.
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