Page 21 - Curriculum Visions Dynamic Book

Zircon
Zircon is the more common name for brilliant sparkling diamond-like crystals of zirconium silicate.
It often forms pyramid-headed crystals in nature. Zircon can be found as tiny crystals in many igneous rocks, where it may vary in colour from brown to green or be colourless. Zircon is very resistant to weathering and
so is also found in sediments such as sandstone, where it often makes up dark grains among the
pale grains of quartz.
The transparent form is called “Matura
diamond”. It has a structure of atoms similar to real diamond. Synthetic zircon is used in jewellery as a
substitute for diamonds (known commonly as CZs, cubic zirconia).
igneous rock: a rock that has solidified from molten rock, either volcanic lava
on the Earth’s surface or magma deep underground. In either case the rock develops a network of interlocking crystals.
metamorphic rock: formed either
from igneous or sedimentary rocks, by heat and/or pressure. Metamorphic rocks form deep inside mountains during periods of mountain building. They result from the remelting of rocks during which process crystals are able to grow. Metamorphic rocks often show signs of banding and partial melting.
Olivine
Olivines are greenish minerals found in many igneous rocks. They are silicates held together with iron and magnesium. They
do not usually form crystals, but instead form grains of translucent, brittle mineral.
They are minerals associated with very high temperature and pressure and are more common in rocks that have been made from materials deep within the earth. The diamond pipes of Kimberley, South Africa, consist mainly
of olivine.
 Cubic zirconia is used in inexpensive jewellery.
 Olivine-rich rock showing the characteristic green colouration.
 Kyanite can form beautiful blue blade-shaped crystals, and is one of the major mineral resources of India.
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