Crystals Rocks Minerals to Tempt and Tantalise You

What are Minerals?

amethyst quartz mineral

Minerals Solid Chemical Compounds

A mineral is an inorganic solid that has occurred naturally through a geological process. Inorganic means it does not contain any living matter. 

Minerals are solid chemical compounds with an internal crystal structure.  This means they're made up of crystals.  A crystalline solid is a mineral.

A crystal structure is an arrangement of atoms that comes together in a highly ordered, repeating symmetrical pattern.  The arrangement forms a crystal lattice.  This lattice forms a crystal.

So crystals are composed of an orderly repeating arrangement of atoms.  If the atoms do not form in this way the substance will not be crystalline.  If it's not crystalline it's not a mineral.

Non crystalline or amorphous solids are known as mineraloids.  Examples include amber which is fossilised tree resin, shungite, opal, pearl, moldavite which is a tektite and obsidian which is a volcanic glass.

examples crystalline and amorphous

Atoms arranged in a crystalline and non crystalline solid

Rocks and minerals are not the same materials.  Minerals are made up of crystals, rocks are made up of several different minerals.

Although there are close to 4000 minerals which have been identified, only about 100 are classified as common.  More than one hundred new mineral varieties are discovered each year.

Most rocks are formed from a small number of the most common 'rock-forming' minerals.  Some of these include quartz, olivine, calcite and pyroxenes.  Peridot is the gemstone variety of olivine, jadeite is a pyroxene.

Identifying some minerals can be very straightforward but others can be very difficult.  Charoite can often be easily identified on sight alone but apatite is more complex.  Throughout history this mineral has been confused for others.  In fact the name apatite comes from the Greek for 'deceive' or 'to be misled'.

When identifying a mineral colour is usually a good place to start. It can also be the most unreliable method because many minerals occur in different colours.

Streak and lustre can help with identification.  Streak describes the colour of a mineral in powdered form.  It never changes and is not always the same as the exterior of the mineral.

Lustre describes the way light interacts with the surface of a rock or mineral.

Mohs scale of mineral hardness was created in 1812 as a way of testing the scratch resistance of one mineral against another.  Diamond which grades 10 is the hardest mineral on the scale.  Talc at number 1 is the softest.  Corundum which grades 9 can scratch quartz which grades 7.  Apatite which grades 5 can scratch fluorite which is 4.

Harder minerals can scratch those which are softer and those of the same hardness can scratch each other.  Hardness is not the same as toughness

Almost everything around us is made up of minerals.  The metals in household appliances and cookware, the materials used to produce tableware.  Copper used for wiring and pipes is a metallic mineral.  Graphite used in pencils is the crystalline form of carbon so it's a mineral.  When subjected to high pressure and temperatures graphite transforms into diamond.

Talcum powder, cosmetics, the pigments in paints and even mobile phones and computers are all made from various minerals.

The materials used in the production of roads and pavements, soil additives used in agriculture and gold, silver and gemstones are all minerals.

From a nutritional perspective the word has a slightly different meaning.  Minerals are required in small amounts to enable our bodies to function normally.  Different amounts are needed by different people depending on age, sex and overall health.

Some of the most important minerals for the human body include magnesium, sodium, calcium, potassium, iron, zinc, fluoride, selenium, manganese and chromium to name just a few.

Article Photo

Our photograph at the top of the page is amethyst. Photograph courtesy of Stan Celestian. The image is clickable and redirects to the original non-compressed photo.

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