Analyze the igneous rocks in Fig. A5.1.1 (and actual rock samples of them if ava

Question

Analyze the igneous rocks in Fig. A5.1.1 (and actual rock samples of them if available). They are depicted at approximately the same size as they are in nature. Beneath each picture, describe the rock's color, composition (what it is made of), a texture (the size, shape, and arrangement of its parts) as well as you can, using your current knowledge and 3 5 Figure A5.11 B REFLECT&DISCUSS; Describe how you would classify the rocks in part A into groups. Be prepared to discuss your classification with your classmates.

Explanation / Answer

1. DIORITE color can range from black, light to dark grey and white, which is composed of sodium-rich plagiocase and lesser amount of Hornblende and biotite. Diorite texture gives the characteristics associated with its grain size and also provides the information about the shape of grains. The basic appearance nature is shiny and this appearance depends on the percentage of impurities in it.

2. OBSIDIAN is usually an extrusive igneous rock whose composition is extremely FELSIC and obsidian consists of Silicon dioxide(SiO2). Obsidian usually forms when molten rock material cools in such a way that atoms are unable to arrange themselves in particular crystalline structure. BLACK is the only and most common colour of obsidian.

3. ANDESITE is a fine grained extrusive igneous rock which are usually light to dark GREY in colour. Andesite is majorly composed of small crystals and Mineral grains which are very small to be observed with normal eye. Andesite is typically found in lava flows which are produced by stratovolcanoes.

4. GRANITE is a most common and well known igneous rock with its grains large enough to be visible with normal eye. Granite is mainly composed of QUARTZ and FELDSPAR with minor amounts of Mica and several other minerals. This very mineral composition gives granite different colours like grey, white, black. In some cases the dark mineral grains are visible throughout the rock.

6. BASALT is a dark or black colour fine grained igneous rock mainly composed of plagioclase and pyroxene minerals. Basalt is very hard in nature and is mostly formed from volcanic lava flow. They are composed of magnesium oxide and calcium oxide and basalts are comparatively rich in iron and magnesium and very low silicon content.

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