identifying rocks? Plz help, in a hurry.....?

Question

1. How do intrusive rocks differ in origin from extrusive rocks?

2. How are polymineralic rocks different from monomineralic rocks? Please give examples of each...

last question..... x)

3. How are all rocks ultimately derived from magma?

Answer 1

Intrusive igneous rocks are formed from magma that cools and solidifies within the earth. (below the surface)

Extrusive igneous rocks are formed at the Earth's surface.

Mono-minerallic rocks are rocks made from one mineral (rock salt).
Poly-mineralic rocks: rocks made from more than one mineral. (pyrite) golden colored mineral that contains a mixture of iron and sulfur and sometimes trace impurities such as gold, nickel, arsenic, and copper.

for your last question these sites may better help you. http://www.classzone.com/books/earth_science/terc/content/investigations/es0602/es0602page02.cfm?chapter_no=investigation
http://www.classzone.com/books/earth_science/terc/content/investigations/es0602/es0602page03.cfm

Answer 2

1-Both of intrusive and extrusive rocks are belonging to igneous rocks, which have been formed by consolidation of molten or partly molten material termed magma. when this magma consolidated relatively slowly at some depth within the crust it will formed intrusive rocks which are characterized by coarse to medium grain size for their mineralogical composition. On the other hand, when the magma erupted to the surface through volcano or other fractures then this magma termed as lava and consolidated rapidly forming micro-crystalline or glass rocks termed as extrusive.
2-Polymineralic rocks formed mainly from more than one mineral as granit , gabbro, granodiorite etc., and the majority of these rock are belonging to igneous and some orthometamorphic rocks.
monomineralic rocks that formed from one minerals and the majority belonging to sedimentary such as sand stone, lime stone roch salt etc., .However ,few igneous rocks are monomineralic as pyroxinite and dunite also serpentinite is orthometamorphic monomineralic rocks.
3-All rocks derived from magma as follow, magma consolidated in the depth or in the surface forming igneous rocks, the rocks affected by T &P forming metamorphic rocks and the both igneous and metamorphic affected by weathering agents forming Sedimentry rocks and so on. and the cycle will repeat

Answer 3

Intrusive harden inside the earth-will have bigger crystals because they hardened slower-example granite
Extrusive-harden outside the earth-extruded as from a volcano so that they have smaller crystals like obsidian-glasslike or like pumice-bubbly full of air holes.
2. Not sure of terms but the word poly means multiple and mono means one so more minerals to one mineral.
3. Lot of ways. Magma must come to or near surface and cool. Could be brought up by volcano, hot spot (Hawaii), mountain building process at edge of input fault (probably a better word for that but then you need to do something, spreading Pacific floor..