Learn More About This Fascinating Subject…

Here in the learning section you’ll find just a taste of some of the knowledge behind rocks, gems and minerals. From how a crystal is formed, or where in the world a mineral type can be found to, what makes one gemstone more valuable than another.

Where Is Amethyst Found?.. How Hard Is Diamond?..

What Makes A Mineral A Gemstone?..

Whether you want some extra info for your homework, or to know just why a treasured piece of jewellery sparkles with colour, you’ll find a good introduction to the subject here.

The Earth on which we live was formed about 4.6 billion years ago, from matter produced by exploding stars. This matter, in the form of hot gases eventually solidified into a sphere of molten minerals which in turn cooled at the surface to form the crust upon which we live.

This relatively thin outer crust contains the primeval fire which is still very active to this day. These very powerful forces are still capable of causing immense damage to the fragile surface of our planet when this energy is violently released in volcanic eruptions and earthquakes.

SEDIMENTARY ROCKSIGNEOUS INTRUSIONMETAMORPHIC ROCK
Laid Down By DepositionMagma Intruding Into Overlying RocksSedimentary / Igneous Rock Altered By Heat And Pressure

Rocks are made of minerals. Only a few minerals are rock forming and most rock is made from a combination of the commonest of these such as feldspars, quartz, mica, olivine, calcite, pyroxene and amphiboles. Most other minerals, of which there are over 3000 different types, are rarely present in quantities large enough to be considered rock forming.

What Are Minerals?

Fluorite

Minerals are made of elements. Elements are simple substances that cannot be broken down into any other substance. The name of an element is written down as a combination of letters called a symbol, eg: sodium is Na; chlorine is Cl. Salt, a combination of sodium and chlorine is thus written as a formula symbol NaCl. Many minerals are made up of large numbers of elements, so their formulas are complex. The most common minerals are those based on silicon and oxygen, Si04.

Sulphur

People value and search for minerals for many different reasons. Most are useful as they are the raw materials of the metals we manufacture into goods. The lead in a pencil is the mineral graphite mixed with clay. Precious metals are used in commerce and other minerals are valued as gems.

Silicate Structure

Minerals are either found in shapeless lumps which we call ‘massive’ or they can form into the special shapes we recognize as crystals. Most minerals form within the spaces between other minerals and grow into rough shapeless masses. However, if they are able to form freely in a hole or cavity in the surrounding rock the mineral takes the form of a crystal and these crystals lined cavities are called geodes, vugs or pockets.

SMOKY QUARTZ

Crystals are solid material in which the atoms are arranged in regular geometrical patterns. The crystal shape is the external expression of the mineral’s regular internal atomic structure. Temperature, pressure, chemical conditions and the amount of space available are some of the things that affect their growth. Many crystallize form watery solutions, some form molten rock as during volcanic eruptions when lava cools rapidly.
Each mineral will always form in a range of crystal shapes. Although there are literally thousands of minerals, their crystal shape can be grouped on the basis of their symmetry into seven systems of three dimensional patterns.

The most striking feature of any mineral is its color. This can be varied and many minerals are a mixture of different colors. What we see as color is a reaction between our brain and eyes. When white light (daylight) falls on a crystal, some of the wave lengths are reflected and some are absorbed.

When some of the waves are absorbed, those that remain make up color that is not white. However, some minerals such as the clear variety of quartz (rock crystal) will take in and reflect out light without changing it, hence they are colorless.

SULPHUR
AnIdiochromatic Mineral

Other minerals are nearly always the same colour because certain light absorbing atoms are an essential element of the mineral’s atomic structure as in Olivine (Peridot), or Sulphur. These minerals are described as Idiochromatic .

CITRINE
An Allochromatic variation of Quartz.

Light-absorbing defects in the atomic structure or impurities in the crystal can produce minerals with a wide variety of colours. These give us red, green, yellow or blue variations of Quartz, Diamond, Beryl, Corundum etc. and are designated as Allochromatic Minerals.

ISAAC NEWTON

Isaac Newton (1642-1727) was the scientist who discovered  that white light can be separated into seven different colours and explained the principal of light dispersion in a prism. Some minerals and crystals radiate colours similar to those seen in a film of oil or a soap bubble. This is called Iridescence and is caused by the interference of white light in the thin surface layers of the mineral.