Obsidian
Obsidian is a natural glass formed when hot lava flows into the surface of the earth and cools quickly. Obsidian has the same chemical composition as granite, but is quenched to make glass rather than cooled slowly to form crystals. Most obsidian is black, or black with red bands. It is brittle. Indians use it to make arrow heads and knives.
Pumice
Pumice is a grayish white natural glass with many tiny holes. It is a valuable scouring, scrubbing, and polishing material in both powered form and as pumice stone. Pumice forms when lava from a volcano flows into the earth's surface or erupts violently into the air. The hot gas-filled lava when cooled quickly to form glass. Many tiny holes remain after the volcanic gasses escape from the cooling lava.
Geode
Geode is a dome-like formation often lined with crystals. Geodes are found in many parts of the world. They average from 2 to 6 inches in diameter. A type of geode called hydrolite, or water stone, contains quartz crystals left when water that contained silica evaporated.
Flourite
Flourite is found all over the world. It used to be called flourspar. It can be found in many different colors, like yellow, purple, pink, blue, green, and colorless. Sometimes flourite is banded with stripes of different colors. Purple and yellow banded flourite is called Blue John. Flourite is a very fragile stone, and can be scratched easily. Because of its lack of hardness, it has been used to make carvings for hundreds of years. It is also used for jewelry.
Amethyst
Amethyst is a purple form of crystalline quartz. It is used for beads and jewelry, and is the birthstone for February. Amethyst is usually found in geodes. It used to be worn to guard against drunkedness and make you serious.
Amazonite
Amazonite is a blue-green variety of microcline. This color is due to lead. Because of the color, amazonite is often mistaken for Jade or Turquoise. It is usually found in India and is sometimes found in the USA, Canada, Russia, Madagascar, Tanzania, and Namibia. Most of the time it is used in jewelry.
Pyrite
Pyrite is usually mistaken for gold, because of its brassy yellow color. This is where it got it's nickname, "Fools Gold". Pyrite got it's name from the Greek word pyr, meaning fire, because pyrite will spark when it is hit with a hammer. Pyrite is found all around the world, The finest specimens come from Spain, Peru, Italy and France.
Quartz
Rock crystal is the transparent form of quartz. It is the most common form because it is found all over the world. This form of quartz is used in lamps, lenses, glass, and clocks. The Greeks thought it was unmelted ice made by the gods. That's where it got its name "krustallos", which means ice.
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