Minerals and Rocks-1 PDF

MINERALS  What is a mineral? A mineral is homogenous, naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. Minerals  About 20 minerals make up more than 95...

MINERALS  What is a mineral? A mineral is homogenous, naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. Minerals  About 20 minerals make up more than 95% of all the rocks in the Earth’s crust  They are formed in the Earth’s mantle(from heat and pressure) – near the surface when oxygen, calcium and carbon combine in the ocean, and when hot, mineral – rich water moves slowly through the cracks in the Earth’s surface Naturally - Occuring Inorganic  It should be made by  The process to natural processes produce a mineral by without the aid of any natural means is organism. extended further by  Any materials that is making sure that no formed in organic material be laboratories or artificial conditions is considered a mineral not considered a mineral. Homogenous Definite chemical Solid composition  We should be able  A mineral must also to see something possess uniformity that is uniform in in its chemical appearance and is composition in the solid state of matter  POLYMORPHS – minerals share a common chemical composition Ordered internal/crystalline structure  A crystalline material is something that has its elemental components arranged in an MINERALOID – does ordered fashion. not contain ordered  The material repeats internal structure this order in a three required in a mineral – dimensional framework that can extend virtually into infinity Physical Properties  Color  Streak  Hardness  Cleavage and Fracture  Crystalline Structure  Transparency  Magnetism  Tenacity  Luster  Odor  Specific Gravity 1. Color  the property used to identify minerals easily  It is a result of the way minerals absorb light 2. Streak  The color of the mineral in powder form 3. Hardness  Refers to the measure of the mineral’s resistance from scratching 4. Cleavage and Fracture  are used to describe how minerals break into pieces  Cleavage – breakage along the crystalline structure where a mineral is likely to break smoothly  Fracture – when it breaks in a direction where there is no cleavage 5. Crystalline Structure  Aka crystal lattice  Tells how a mineral’s crystals are arranged  Crystal solid – form a regular repeating three – dimensional crystal lattice  Amorphous solid – forms aggregates that have no particular order or arrangement 6. Transparency  Aka diaphaneity  Indicates the extent of light that can pass through the mineral 7. Magnetism  Ability of minerals to attract or repel other minerals 8.Tenacity  The level of resistance or reaction of minerals to stress such as crushing, bending , breaking or tearing  It can tell if a mineral is brittle malleable, elastic etc. 9. Luster  Refers to the reaction of a mineral to light  Determines how brilliant or dull the mineral is 10. Odor 11. Specific Gravity  Distinct smell of a  Measure of the mineral that is density of a mineral usually released  Determines how from a chemical heavy the mineral is reaction when by comparing its subjected to water, weight to that of heat, air or friction water Chemical Properties  Silicate class  Carbonate class  Sulphate class  Halide class  Oxide class  Sulphide class  Phosphate class  Native Element class 1.Silicate 2. Carbonate  Largest and most  Mostly found abundant group deposited in marine containing silicon environments and oxygen with  Formed from shells some aluminium, of dead plankton magnesium, iron and other marine and calcium organisms 3. Sulphate 4. Halide  Forms in areas with  Contains natural high evaporation salts rates and where  Usually form in salty waters slowly lakes, ponds, and evaporate other landlocked seas such as the Dead Sea 5. Sulphide 6. Phosphate  Has important  Contain minerals metals like copper, with phosphorous lead and silver which are economically significant 7. Native Element  Contains metals and intermetallic elements, semimetals, nonmetals or natural alloys and constituents of a few rare meteorites  What is a rock? A rock is a naturally occurring aggregate of minerals and/or other rock fragments ROCK CYCLE  Rock classification Igneous Sedimentary Metamorphic  Igneous rocks Igneous rocks form when molten rock (magma) cools and solidifies, with or without crystallization,either below the surface as intrusive (plutonic) r ock s or on t h e s ur f a c e a s extrusive (volcanic) rocks. IGNEOUS ROCKS  Texture Texture refers to the physical appearance or character of a rock, such as grain size, shape, and arrangement. Igneous rocks that crystallize slowly beneath the Earth's surface, typically have visible individual minerals. Extrusive igneous rocks tend to cool much more rapidly, and the minerals grow quicker and can not get as large. They thus have a sugary or fine grained texture.  Texture coarse coarse coarse Glassy/fine  Mineralogic contents ·felsic rock, with predominance of quartz, alkali feldspar and/or feldspathoids: the felsic minerals; these rocks (e.g., granite) are usually light colored, and have low density. ·mafic rock, with predominance of mafic minerals pyroxenes, olivines and calcic plagioclase; these rocks (example, basalt) are usually dark colored, but not always, and have a higher density than felsic rocks. ·ultramafic rock, with more than 90% of mafic minerals (e.g., dunite)  Sedimentary rocks Sedimentary rocks are classified by the source of their sediments, and are produced by one or more processes that follow: SEDIMENTARY ROCKS  Sedimentary rocks Clastic sedimentary rocks are composed of fragments of older rocks that have been deposited and consolidated · boulders greater than 25.6 cm · cobbles 6.4 to 25.6 cm · pebbles 2 mm to 6.4 cm · sand 1/16 mm to 2 mm · silt 1/256 mm to 1/16 mm · clay less than 1/256 mm  Sedimentary rocks Chemical sedimentary rocks form when minerals precipitate from a solution, usually sea water. Halite and gypsum are examples of minerals that precipitate from aqueous solutions to form chemical sedimentary rocks. Biochemical sedimentary rocks are composed of accumlations of organic debris. Coal and some limestones are examle of biological sedimentary rocks.  Metamorphic rocks Metamorphic rocks are the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat (greater than 150 degrees Celsius) and/or extreme pressure causing profound physical and/or chemical change. The protolith may be sedimentary rock, igneous rock or another older metamorphic rock. METAMORPHIC ROCKS Foliation refers to flat or wavy planar features (looking like layers) caused by the alignment of platy minerals such as mica. Foliation may also look like alternating bands of light and dark minerals. Nonfoliated rocks have interlocking grains with no specific pattern. They are classified based on composition, and this usually depends on the type of rock it originally formed from. Homogeneous quartz  characteristic chemical composition Sulphur S  characteristic chemical composition Quartz SiO2  characteristic chemical composition Tourmaline (Ca,K,Na)(Al,Fe,Li,Mg,Mn)3 (Al,Cr, Fe,V)6(BO3)3(Si,Al,B)6 O18(OH,F)4