• These minerals contain metal content and can be sub-divided into three types: Precious metals, ferrous metals, and non-ferrous metals.
• These minerals do not contain metal content. Sulphur, phosphates and nitrates are examples of non-metallic minerals.
(1) External crystal form
(10) Specific gravity
• earth’s crust is composed of rocks. A rock is an aggregate of one or more minerals. Rock may be hard or soft and in varied colours.
• Petrology is science of rocks. A petrologist studies rocks in all their aspects viz., mineral composition, texture, structure, origin, occurrence, alteration and their relationship with other rocks.
• As igneous rocks form out of magma and lava from interior of earth, they are called primary rocks.
• word sedimentary is derived from Latin word sedimentum, which means settling. Rocks [igneous, sedimentary and metamorphic] of earth’s surface area are exposed to denudational agents and are broken up into various sizes of fragments.
• word metamorphic means change of form. These rocks are formed under action of pressure, volume & temperature [PVT] change.
• Mechanical disruption and reorganisation of original minerals within rocks due to breaking and crushing without any appreciable chemical changes is known as dynamic metamorphism.
• Rocks do not remain in their original form for long but may transform.
• Igneous rocks are primary rocks and other rocks [sedimentary and metamorphic] form from these primary rocks.
• Sedimentary rocks themselves can turn into fragments and fragments can be sources for formation of sedimentary rocks.
• crustal rocks [igneous, metamorphic and sedimentary] once formed may be carried down into mantle [interior of earth] through subduction process [parts or whole of crustal plates going down under another plate in zones of plate convergence] and same meltdown due to increase in temperature in interior can turn into molten magma, source for igneous rocks.