Do not place the molten mixture near an open flame or spark! Using tongs, place one test tube into the warm water and one into the cold water at the start of class. Begin your lecture on crystal size and morphology. After about ten to fifteen minutes depending on the temperature of the warm water , remove the test tubes from the beakers.
Compare the size of the crystals. You may need to use a magnifying glass in order to see the crystals clearly; rotating the tube to catch specular reflection may also help.
Do you notice anything unusual about the crystals in the tube which was placed into cold water? HINT: Is there a color change from top to bottom of the test tube?
Why did the crystals grow to different sizes? Does crayon color have any effect on the crystal size? What about the relative amount of mothballs? Based on what you have discovered, can you explain why ice cream must be churned? Try making ice cream without churning! This demonstration was adapted from Jackson, J. Mafic basaltic : rocks have higher amounts of ferromagnesium minerals and less silica and feldspar.
Rocks are dark in color, black or dark gray. Ultramafic : highest amount of ferromagnesium minerals and least amount of silica. Rocks are usually a dark green to green-black. Igneous rocks are classified by both texture and composition. You will learn to identify common igneous rocks in lab. Geology home. Sedimentary Rocks. Metamorphic Rocks. Volcanoes Volcanic Eruptions Volcanic Landscapes.
Igneous Rocks Igneous rock is formed from the cooling of a magma. As magma cools igneous rock is formed. There are two types of igneous rock: 1 Extrusive : magma reaches the surface of the Earth before cooling and the lava cools rapidly. Textural terms for igneous rocks: 1. This means that we get two main types of igneous rock, extrusive and intrusive, as shown in the table:. Extrusive igneous rocks form from magma that erupted onto the surface as lava , where it cooled quickly.
On the other hand, intrusive igneous rocks form from magma that cooled slowly, deep underground. Igneous rocks do not contain any fossils. This is because any fossils in the original rock will have melted when the rock melted to form magma. You may have done an experiment at school with a substance called salol. If molten salol cools slowly, you get big crystals.
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