Semiblack or gray opal – translucent to opaque with play-of-color against a light to medium gray bodycolor

Crystal opal – transparent to semitransparent with colorless body and strong play-of-color

Black crystal opal – transparent to semitransparent with dark bodycolor and strong play-of-color

Fire opal – transparent to semitransparent with yellow, red, or orange to brown bodycolor, with or without play-of-color; also called Mexican opal, gold opal, or sun opal

Cherry opal – fIre opal with a red bodycolor

Jelly or water opal – colorless, transparent to semitransparent with little or no play-of-color

Noble or precious opal – opal with play-of-color

Names based on the appearance of the play-of-color

Pinfrre or pinpoint opal – small close-set patches of color

Harlequin or mosaic opal – broad, angular, close-set patches of color

Flame opal – sweeping reddish bands or streaks that shoot across the stone

Flash opal – play-of-color shows in sudden flashes that quickly disappear or change as the stone is moved

Peacock opal – play-of-color is predominantly blue and green

Lechoses opal – green play-of-color only

Less common names

Contra-Iuz opal – a rare type of transparent opal showing strong play-of-color in both reflected and transmitted light

Boulder opal – a thin seam of opal with play-of-color occurring in ironstone matrix; the opal is cut on top with the ironstone matrix as a backing that adds strength and a dark background

Matrix opal or opal in matrix – thin seams or spots of opal with play-of-color randomly scattered throughout matrix; also called mass opal

Louisiana opal – a rock principally composed of quartz, opal, and pyrite

Opalized bone – bone replaced by opal; dark brown, opaque with small patches of play-of-color in the cellular structure of the bone

Opalized wood – wood replaced by opal; also called xylopal

Opalized shell – shell replaced by opal

Oolitic opal – play-of-color acts as a background for numerous black or brown spherical inclusions that have the appearance of fish eggs (roe) and are scattered throughout the stone

Tabasheer – amorphous opal-like silica found in the joints of some types of bamboo

Common opal

Common opal – translucent to opaque opal without play-of-color; also called potch

milk opal – white common opal

Onyx opal – banded opal

wax opal – yellowish opal with a waxy ,luster

Prase opal – translucent to opaque green common opal; yellowish green material resembling chrysoprase chalcedony is also called chrysopal

Moss opal – common opal with inclusions that look like moss

Cachalong opal – bluish white, porous, translucent to opaque, porcelain-like; also called Kalmuck agate opal

Girasol opal – semitransparent to translucent with a moving billowy light resembling moonstone

Hyalite – transparent colorless to translucent white; also called water stone

Hydrophane – common opal that when soaked or heated in water or oil shows play-of-color; also called magic stone

Wood opal – dark brown to black and opaque, an opal pseudomorph after wood; also called zeasite

Iron opal – yellow to red common opal

Slocum stone : Magnification, RI, SG (possibly)

Fluorite : SG, cieavage, RI (possibly)

Chalcedony : RI, SG

Plastic imitation (with play-of-color): SG, hardness