Opal

	What is it and where is it formed? Opal is a gemstone and the birthstone for October. Opals can form anywhere but are mostly found in places where there hot springs. It is sedimentary and is fluorescent a lot of times. It is a very easy stone to break.
	How and where is it mined? Opals are mined using open pit surface mining. Sometimes opal mining areas are rented for the day. People can come in, mine the open pits, and take what they find. Opals are found in: Mexico, Australia, England, Czech Republic, and Western United States.
	What is it used for? Opals are used in jewelry even though the stones crack easily. They are also used for collections of gemstones.

Opals are cut with rounded curves so that the colors will shine through. This is called opalescence.

Mineral Characteristic	What the mineralogists say	Kid's Guide: What it REALLY means!
Chemical Symbol	SiO₂∙n(H₂O)	It has oxygen, silicon, and hydrogen in it.
Color	White, colorless, light yellow or red, or gray	Opal color depends on how pure the stone is. Most stones look white but have an iridescent shining of other colors, too. If they show colors, they are called precious opals.
Streak	White	If you crushed this stone, it would make white dust every time.
Transparency	Transparent to translucent	You can see through some of them clearly. Others would be blurry to look through.
Luster	Vitreous - pearly	The stone would look glassy or sometimes shimmery like a pearl.
Cleavage	None	It doesn’t break evenly in a pattern each time it is broken.
Fracture	Conchoidal	If it is shattered, the pieces have smooth surfaces.
Magnetism	None	It is not attracted to and will not attract a magnet.
Hardness	6	It is hard enough that it might scratch glass a little. It is upper middle on the Mohs scale of hardness.
Specific gravity	2	If you held an opal, it would seem light for its size.
Crystal Shape	None	It is not a crystal mineral.

Photo by Eric Greene, courtesy of Treasure Mountain Mining

Links:

	Edrin Corporation: All about opals
	Gem Gallery
	Desert USA
	Famous Opal stones

Rough opals

Citations:

“Opal.” Raintree Illustrated Science Encyclopedia. 1991 ed.

“Opal.” World Book Encyclopedia. 2000 ed.

“Rick.” "Ebay Question for item #6598488700 [Opal]." E-mail to Club Web. 19 Jan 2006.