Generally, a rock that is black is made up of crystals that are rich in Iron and Magnesium. This is NOT the case with this rock (____________), which is instead rich in Silicon and Aluminum.  Its pitch-black, shiny appearance is due to the ABSENCE of crystals - it is pure GLASS. It forms from magma that is so gooey that elements cannot "move around" through it to arrange themselves into crystals.Group of answer choicesobsidiangranitebasaltpumice

If a magma that is rich in Silicon and Aluminum cools over thousands of years underground, it forms Granite. If it cools quickly when it erupts from a volcano, it forms Rhyolite.If a magma that is rich in Iron and Magnesium cools over thousands of years underground, it forms Gabbro (which is sold as "black granite" at home improvement stores). If it erupts from a volcano, it also forms a black rock, but because it cools quickly, the crystals can only be seen under the microscope/ This rock is  _________Although _________ not common on continents, this rock is the most common rock on Earth's surface, because it forms the ocean floor. It is also the rock that makes up the Hawaiian islands, famous for their beautiful volcanoes and river-like lava flows.Group of answer choicesobsidiangranitebasaltpumice

This rock, _______________, is made of  "welded" volcanic ash (it is very hot when it settles). It is commonly used to make cosmetic exfoliants. It works well as an abrasive because volcanic ash is made up of tiny shards of glass.Group of answer choicesobsidiangranitebasaltpumice

Quartz can be classified as which of the following?AmineralBigneous rockCmetamorphic rockDsedimentary rock

What type of rock is quartzite?

Name the three rock forming minerals.