Page 11 - Curriculum Visions Dynamic Book

Ruby set in a green groundmass of smaller crystals
gemstone: a wide range of minerals valued by people, both as crystals (such as emerald) and as decorative stones (such as agate). There is no single chemical formula for a gemstone.
ion: an atom, or group of atoms, that has gained or lost one or more electrons and so developed an electrical charge.
mineral: a solid substance made of just one element or chemical compound. Calcite is a mineral because it consists only of calcium carbonate, halite is a mineral because it contains only sodium chloride, quartz is a mineral because it consists of only silicon dioxide.
silicate: a compound containing silicon and oxygen (known as silica).
Ruby (aluminium oxide)
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. However, when it occurs with small amounts of another element, chromium, the
colour changes to somewhere between pale rose and deep red.
Haematite (iron oxide)
This is the name for the most widespread form of iron ore. It can be found as concretions (lumps), but it is most often
found in rocks once deposited by rivers or the sea. Deep red rocks often tell of the iron oxide colour of
haematite. Most such rocks were formed in those parts of the tropics with a wet and a dry season. During the wet
season the minerals were eroded from the land and washed to inland basins, deltas or coasts. During
the dry period the water evaporated and the sediments dried out, oxidising iron
compounds to iron oxide. These rocks are often referred to as “red beds” and are usually
fine-grained materials such as shales.
Haematite amongst quartz crystals
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