Opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Because of its amorphous character, it is classed as a mineraloid, unlike crystalline forms of silica, which are classed as minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. Opal is the national gemstone of Australia.There are two broad classes of opal: precious and common. Precious opal displays play-of-color (iridescence), common opal does not. Play-of-color is defined as "a pseudochromatic optical effect resulting in flashes of colored light from certain minerals, as they are turned in white light." The internal structure of precious opal causes it to diffract light, resulting in play-of-color. Depending on the conditions in which it formed, opal may be transparent, translucent or opaque and the background color may be white, black or nearly any color of the visual spectrum. Black opal is considered to be the rarest, whereas white, gray and green are the most common.
List of Pinterest Opal images & Opal pictures
List of all Pinterest Opal images and pictures. Browse Pinterest Opal ideas
Details about 1.01 Carat Australian Black Opal Engagement Ring 37 Diamonds 18K Yellow Gold
Size 6.25. Free Gift Bag/Box with every order! Every Opal piece is Unique. You won't find two exactly identical opal gems because of their unrepeatable play-of-color. Being worn frequently can help opal to acquire the necessary humidity from the air as well as from the skin. | eBay! #designerjewelry
Details about Simple Marquise Cut Australian Solid Opal Ring 925 Sterling Silver Rainbow Color
Oval Australian Rainbow Doublet Black Opal Engagement Ring 18k Yellow Gold with Beautiful Play-of-Color. Size 6.5. Free Gift Box with Every Opal Order! Natural Australian Doublet Opal, 0.78 ct. Every Opal piece is Unique. | eBay!
Introduction to the Different Types of Australian Opal
Did you know that 90% of the worlds Opal is found in Australia? You also might not realise that depending on which Opal mine you are at you will find very different types of Australian Opal. You can find black Opal in New South Wales, white Opal in Queensland and boulder and matrix Opal in South Australia and Queensland.