Many a times we come across terms which seem to convey the same meaning though in reality they are poles apart. Rock and mineral are too such words which to a general person appears same in meaning. However these two have very stark difference between them. Before going into the key difference between the two let’s firstly understand their meanings.
MINERALS – Minerals are the naturally occurring inorganic substances found mainly in rocks which have high economical values and are used for various purposes in our daily life. Some of the notable metals gold, iron, copper, silver, zinc and many others which are extracted from their minerals.
Minerals are formed through various geological formations underneath the earth. They have a fixed chemical composition, nearly ordered atomic structures and having specific physical properties.
Rocks – Rocks are geological formations occurring in the earth. They consist of inorganic minerals as well as organic substances. They make up the earth’s crust and their composition is never fixed. Rocks vary in size from tiny hills to huge mountains. Their shape too is not fixed and can be found in both liquid and solid state. Usually rocks below the earth are liquid in form, ex – magma , lava are all rock forms and are liquid in state.
Difference between Minerals and Rocks :-
TYPES OF ROCKS AND MINERALS:-
Rocks can be broadly classified into 3 types –
1- Igneous rocks :- Igneous rocks are formed when the hot molten magma below the earth surface rises up to the surface of the earth and cools down. Together with metamorphic rocks they make up 90-95% of the earth crust. (ex – granite).
2- Sedimentary rocks :- This type of rocks are formed from the deposits of sand and gravels. This rocks are compressed enough to form rock. Sedimentary rocks have a considerable amount of fossils deposited in them. (ex – limestone)
3- Metamorphic rocks – This type of rocks are formed due to changes occurring in the pre-existing rocks under the effect of temperature and pressure. Higher the temperature and pressure, larger would be the grain size. (ex – marble)
Minerals – Minerals can be broadly classified into two –
- Metallic minerals – These are the type of minerals occurring usually in solid form, having fixed shape and composition. They have a characteristic lustre/shine in appearance. (ex- iron)
- Non-Metallic minerals – These are the type of minerals that do not have a metallic lustre and break away easily. (ex- limestone)
Identifying Minerals –
Minerals are identified through the properties they possess. Every mineral shows significant difference in the properties through which they are recognised by the mineralogist. The following properties are used to identify a particular mineral –
1- Colour – It is the most easily identifiable property of a mineral and is used to identify a particular mineral. However it is very difficult to identify a mineral purely on the basis of the colour, as many minerals have the same colour. (ex – gold has golden colour)
2- Streak – It is the colour of the powder obtained on rubbing the mineral on an unglazed porcelain plate. It is more reliable than colour in identification of a mineral. For example, hematite and galena can are dark grey in colour, but hematite has a red streak and galena has a grey streak.
3- Lustre – Lustre refers to the property of a mineral which depends on how effectively that mineral reflects the light falling on it. ( ex – diamond has very high lustre)
4- Density – Density refers to mass per unit volume. Usually metallic minerals are denser than non-metallic minerals.
5- Hardness – Hardness is defined as the ability of a material to resist scratch. Mohr’s chart is used to classify minerals on the basis of hardness , with the hardest mineral –black diamond at the bottom (Mohr value -10) & the lightest mineral at the top of the chart – Talk ( Mohr value -1)
6- Besides this there are other properties like cleavage, fracture, magnetism, radioactivity which are also used to identify minerals.