Aim:Aim: What are Igneous Rocks?

I. RocksRocks – made up of more than one mineral. Rocks are classified according to how they were formed. Igneous, sedimentary, metamorphic.A. IgneousIgneous – rocks that form from magma (lava) when it cools and hardens.1.1.MagmaMagma – hot, molten rock.

2.2.LavaLava – magma that reaches earth’s surface.

3. Rate of cooling can be determined by crystal size.

a.a.Large crystalsLarge crystals – magma cooled slowly inside earth. Intrusive or plutonic rocks.

b.b.Small crystalsSmall crystals – lava cools quickly on surface of earth. Extrusive or volcanic rocks.

4. Igneous rocks are classified according to crystal size and color. (go to page 6 of Reference Tables)

GRANITE

RHYOLITE

a.a.Felsic rocksFelsic rocks – light in color, low in density, and rich in feldspar and silica.

b.b.Mafic rocksMafic rocks – dark colored, high in density, and rich in magnesium and iron.

1. According to the E.S.R.T.’s, which of these is a fine-grained, dark colored igneous rock? a) basalt b) diorite c) shale d) granite

2. Large crystals in a rock show that the rock formed by:

Questions

3. Sand collected from a beach contains a mixture of pyroxene, olivine, hornblende, and plagioclase feldspar. According to the E.S.R.T.’s, what can we conclude about the rock that it came from?

a) it was mafic in composition b) it was relatively low in density c) it contained only light-colored minerals d) it was either granite or rhyolite.

4. According to the E.S.R.T.’s, what is the approximate percentage of plagioclase feldspar in igneous diorite? a) 10% b) 30% c) 60% d) 90%

5. Which characteristic of an igneous rock provides the most information about how it formed?

a) Color b) texture c) streak d) hardness

http://www.eram.k12.ny.us/education/sctemp/190b1c88a4f2b19bc1aff975efb87c7c/igneous.swf