Igneous Rock: Obsidian

Obsidian is a a natural glass.  During volcanic eruptions the way in which the magma cools has an effect on the texture of igneous rocks.  Three factors that affect the crystal size include: (1) the rate at which the magma cools; (2) the amount of silica present; and (3) the amount of dissolved gases in the magma.

The glassy texture seen in obsidian is caused by rapid cooling.  The unordered ions are frozen before they could unite into an orderly crystalline structure. Obsidian was used by the native Americans to create cutting tools and arrowheads.

Minerals: Building Blocks of Rocks

This is the mineral feldspar

This is the mineral mica

This is the mineral galena

This the mineral quartz

This is the mineral hornblende
 

This is the mineral calcite

Maps

This is an isarithmic map. It shows a certain phenomenon defined by smooth and continuous lines.

This is a choropleth map.  It shows statistical data for predefined regions

This is a proportional symbol map. The different size symbols represent data relative to each location. 

This is a dot density map. A dot can represent a certain number range, and placed in a certain location to show that phenomenon. 

This is a map I created based on how rural or urban  each county in Georgia  is.