Observation

The expected answers were:

• Gabbro
• Obsidian
• Diolerite
• Microgranite
• Porhpyries
• Peridotite

(b) (i) Plutonic Igneous rock is an intrusive igneous rock. This is rock which has cooled and solidified deep on the earth crust. They have large crystals due to slow cooling. They are exposed to the surface after a prolonged erosion. They form batholiths, sills, dykes, laccoliths, stocks etc Notable examples include granite, gabbro, diorite etc.
(ii) Volcanic igneous rock is an extrusive igneous rock. This is rock formed from magma clevas that reached the surface of the earth before cooling and solidifying. They are crystalline and fine grained because they have cooled rapidly. Notable example include and ersite, rhyolite, basalt etc.
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(c) 
- Crystalline in nature
- Non-stratified rocks i.e. they do not occur in layers
- Resistant to erosion
- Usually hard