1. Identifying Minerals Rock-Forming Minerals
Over 2000 known minerals, many are rare
Common minerals are rock-forming minerals
Most R-F minerals are silicate
The minerals are identified by their physical properties
The study of minerals is mineralogy

2. Identification by Inspection
Colour is the first and most easily observed mineral property
Colour is the least useful property, because many different minerals have similar colours
Traces of impurities can turn colourless minerals into coloured minerals
Luster is the way the mineral shines in reflected light
Lusters are either metallic or nonmetallic
Nonmetallic luster can be vitreous (like glass), pearly, resinous, or glassy.
Diamond has adamantine luster.
Other terms are greasy,oily, dull, and earthy

3. Identification by Tests
The streak of a mineral is the colour of its powder, obtained by rubbing it on an unglazed white tile called a streak plate.
The cleavage of a mineral is its tendency to split easily or separate along flat surfaces
Some minerals tend to break along non-cleavage surfaces, called fracture
The hardness of a mineral is its resistance to being scratched, diamond is the hardest, talc is the softest
Friedrich Mohs devised the hardness scale from one to ten

5. Specific Gravity
Specific gravity is the ratio of the weight of a mineral to the weight of an equal volume of water
S-G tells you how many times as dense as water the mineral is
Nearly all minerals are denser than water
Their specific gravities are greater than 1
The weight of the mineral is found by weighing it in air
Then the mineral is weighed underwater
The second weighing indirectly gives the weight of an equal volume of water
The sample weighs less underwater due to buoyancy
Archimedes’ principle states that this loss in weight is equal to the weight of the displaced water
Specific gravity = weight of sample in air weight of equal volume of water
= weight of sample in air
loss of weight in water

6. Acid Test Calcite is the principle mineral in limestone and marble
Calcite is calcium carbonate, and a drop of weak hydrochloric acid will cause it to fizz.
The bubbles are carbon dioxide gas