Minerals

A Mineral is a naturally occuring, inorganic, solid, definite chemical composition with a crystaline structure.

Examples of different minerals.

Properties of Minerals

• Lustre - The way a mineral shines and reflects light from its surface - which is different from its actual colour. Lustre can vary from dull to glassy (vitreous).

• Colour - What the colour of the mineral looks like to the naked eye. Colour is not the most reliable property for identifying a mineral.

• Hardness - The hardness of the mineral is its ability to be scratched by other minerals or scratch other minerals. Hardness of minerals are classified from 1 (softest) to 10 (hardest) on Moh's Hardness Scale. For example, Talc is the softest mineral, so it is a 1 on Moh's Hardness Scale. All other minerals will be able to scratch Talc.

• Streak - Streak is the colour of a fine powder of a mineral. A streak test can be done by rubbing a mineral across an unglazed porcelain streak plate. Streak is more reliable than the colour of the mineral for identification. The colour of a mineral's streak is not always the same as the colour of the mineral.

• Density - Density is also known as specific gravity. It is the weight of a substance in relation to an equal volume of water. Most minerals have a density of 2.5-3.5, although some may be more or less.

• Cleavage - Cleavage is the tendency of some minerals to break along certain planes.

   

• Magnetism - The ability of a mineral to attract a magnet.

   

• Crystal Shape - the way atoms arrange themselves in a regular, orderly, and periodically repeated pattern in order to form a crystal.

• Reaction to Hydrochloric Acid - If a mineral reacts with Hydrochloric Acid, then the mineral is considered acidic.

   

• Fluorescence - If a mineral is fluorescent, then it will have a neon appearance when placed under ultraviolet light

Examples of fluorescent minerals.

Moh's Hardness Scale

    Moh's Hardness Scale is a scale which classifies the hardness of minerals, with 1 being the softest and 10 being the hardest. All minerals fall within this range. The scale (below) is based on ten common minerals. Minerals with a higher number can scratch all minerals that have a lower number.

 

1 - Talc

2 - Gypsum

3 - Calcite

4 - Fluorite

5 - Apatite

6 - Feldspar

7 - Quartz

8 - Topaz

9 - Corundum

10 - Diamond