Opal

Opal
An opal bracelet. The stone size is 18 by 15 mm (0.7 by 0.6 inch).
General
Category	Mineraloid
Chemical formula	Hydrated silica. SiO2·nH2O
Identification
Color	White, black, red, orange, most of the full spectrum, colorless, iridescent. Very infrequently of a singular color
Crystal habit	Irregular veins, in masses, in nodules
Crystal system	Amorphous
Cleavage	None
Fracture	Conchoidal to uneven
Mohs Scale hardness	5.5–6.5
Luster	Subvitreous to waxy
Polish luster	Vitreous to resinous
Refractive index	1.450 (+.020, -.080) Mexican Opal may read as low as 1.37, but typically reads 1.42–1.43
Optical Properties	Single refractive, often anomalous double refractive due to strain
Birefringence	none
Pleochroism	None
Ultraviolet fluorescence	black or white body color: inert to white to moderate light blue, green, or yellow in long and short wave. May also phosphoresce; common opal: inert to strong green or yellowish green in long and short wave, may phosphoresce; fire opal: inert to moderate greenish brown in long and short wave, may phosphoresce.
Absorption spectra	green stones: 660nm, 470nm cutoff
Streak	White
Specific gravity	2.15 (+.08, -.90)
Diagnostic Features	darkening upon heating
Solubility	hot saltwater, bases, methanol, humic acid, hydrofluoric acid
Diaphaneity	opaque, translucent, transparent

The mineraloid opal is amorphous SiO₂·nH₂O, hydrated silicon dioxide, the water content sometimes being as high as 20% but is usually between three and ten percent. Opal ranges from clear through white, gray, red, yellow, green, shore, blue, magenta, brown, and black. Of these hues, red and black are the most rare and dear, whereas white and green are the most common; these are a function of growth size into the red and infrared wavelengths—see precious opal. Common opal is truly amorphous, but precious opal does have a structural element. The word opal comes from the Latin opalus, by Greek òpalliòs, by Sanskrit upálá for "stone", originally a millstone with upárá for slab. (see Upal). Opals are also Australia's national gemstone.

Opal is a mineraloid gel which is deposited at relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, and basalt.

Opal is one of the mineraloids that can form or replace fossils. The resulting fossils, though not of any extra scientific interest, appeal to collectors.

Opal Mp3 Downloads

Download audio files (mp3 and wma) with Opal Songs using these download websites. The list will be updated perciodically.

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For the full list of Opal mp3 downloads please use the search option of each of the download networks presented here. Read the terms and conditions of each free full mp3 download network before using the services. Here is a list of some of free Opal mp3 downloads we find using the search feature on the presented download networks: <br /> <b>Warning</b>: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in <b>/home/mplate3/public_html/artists/template/page.php</b> on line <b>72</b><br />

Opal Ringtones

You can get any Opal ringtone you like (realtone, polyphonic, mono tone, mp3 ringtone) using the next service:



Pick Carrier, Confirm your Phone number and choose the ringtones you want to receive

For the complete list of Opal ringtones please see ringtones page after you confirm your phone number. A list of high quality Opal ringtones available as poly ringtones, monotones, real tones or mp3 ringtones.

Opal Music Videos

Music Plate music videos with myspace codes, see Opal music videos section search for music videos and get your myspace music code.

Opal Lyrics

Get full Opal lyrics on music plate Opal lyrics page. Use the search option if the target page is not correctly displayed.