Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Limonite
Limonite is an amorphous brown iron oxide ore, the rust-colored material behind ochre pigments and bog iron.
mineral
Opal
A hydrated silica gemstone famous for its shimmering play-of-color, ranging from white and black opal to fiery orange fire opal.
gemstone
Ice Opal
A clear, glassy, near-colorless opal resembling ice, sometimes with subtle internal flashes of play-of-color.
gemstone
Star Opal
Opal that displays a radiating, star-shaped pattern of play-of-color, a rare and prized internal structure.
gemstone
Opalite
A man-made opalescent glass that glows milky blue in reflected light and warm orange when backlit, often sold as a crystal.
crystal
Red Opal
An opal with a deep red body color, often a variety of Mexican fire opal, prized for its warm, glowing intensity.
gemstone
Mint Opal
A soft mint-green variety of common opal, usually opaque and colored by trace copper or nontronite inclusions rather than play-of-color.
gemstone
Moss Opal
A common opal containing moss- or fern-like mineral inclusions that resemble plants suspended in a pale silica body.
gemstone
Wood Opal
Fossil wood replaced by opaline silica that preserves wood grain, occasionally showing the play-of-color of precious opal.
gemstone
Gold Opal
A golden-toned opal ranging from translucent common opal to precious stones flashing color against a warm yellow body.
gemstone
Pink Opal
A soft pink common opal, most famously from Peru, valued for its gentle pastel color rather than play-of-color.
gemstone
Welo Opal
Bright play-of-color opal from the Wollo Province of Ethiopia, mostly hydrophane and known for broad, vivid fire.
gemstone
Blue Opal
A soft blue common opal, famously from Peru, valued for its serene sky-to-teal color rather than play-of-color.
gemstone
Milk Opal
An opaque to translucent milky-white common opal valued for its soft porcelain-like color rather than play-of-color.
gemstone
Fire Opal
A translucent to transparent opal in warm yellow, orange, and red tones, prized for body color rather than play-of-color.
gemstone
Bone Opal
Fossil bone in which opal has replaced the original tissue, sometimes showing play-of-color, a rare collector fossil.
gemstone
White Opal
The most common precious opal, with a pale milky body that shows softer pastel flashes of play-of-color throughout.
gemstone
Water Opal
A transparent, colorless opal that looks like water or jelly, sometimes flashing subtle play-of-color from within.
gemstone
Shell Opal
Fossil shells whose original material has been replaced by opal, preserving ancient marine forms in common or precious opal.
gemstone
Lemon Opal
A bright lemon-yellow opal, usually common opal, valued for its cheerful citrus color and translucent glow.
gemstone
Jelly Opal
A translucent, gelatinous-looking opal whose transparency gives floating, glowing play-of-color a watery, jelly-like appearance.
gemstone
Flame Opal
A glowing orange-to-red opal whose warm body color resembles flame; some stones add flashes of play-of-color.
gemstone
Orange Opal
A vivid orange opal, classically Mexican fire opal, prized for its bright, fiery body color that glows when backlit.
gemstone
Flash Opal
A precious opal whose play-of-color appears as broad rolling flashes of spectral color that shift as the stone moves.
gemstone