Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Rhodonite
A rose-pink manganese silicate marbled with black veins, prized as a tough ornamental and occasionally faceted gemstone.
mineral
Bone Opal
Fossil bone in which opal has replaced the original tissue, sometimes showing play-of-color, a rare collector fossil.
gemstoneCandle Quartz
A quartz with a main point surrounded by many smaller crystals along its sides, resembling melted candle wax, mainly from Madagascar.
crystal
Petrified Wood
Ancient wood whose organic tissue has been replaced by silica, preserving the grain, rings, and structure of the original tree in stone.
sedimentary
Fossil Opal
Fossil material whose original substance has been replaced by opal, preserving ancient shapes in common or play-of-color opal.
gemstone
Shell Opal
Fossil shells whose original material has been replaced by opal, preserving ancient marine forms in common or precious opal.
gemstone
White Agate
A white to grayish banded chalcedony, the natural base color of much agate and the substrate for many dyed stones.
gemstone
Goldmanite
A green, vanadium-dominant garnet that forms in vanadium-rich metamorphic and sedimentary rocks, notably in uranium-vanadium districts.
mineral
Spinel
A durable magnesium aluminum oxide gem that occurs in many colors and was long mistaken for ruby.
gemstone
Slawsonite
A rare strontium-dominant feldspar, the strontium analogue of paracelsian, found in metamorphosed strontium-rich and manganese-bearing rocks.
mineral
Stephanite
A black metallic silver antimony sulfide, historically a notable silver ore known as brittle silver ore.
mineralMocha Agate
A pale translucent chalcedony threaded with brown-black manganese and iron dendrites that mimic tiny ferns, mosses or landscapes.
gemstone
Elestial Quartz
A quartz with a complex skeletal, layered surface of many terminations and etched recesses, also called skeletal or jacare quartz.
crystalPipestone
A soft, fine-grained red metamorphosed claystone, sacred to many Native American peoples and carved into ceremonial pipes.
metamorphic
Rainbow Tourmaline
Tourmaline showing many color zones in a single crystal, often revealing spectacular concentric patterns when sliced.
gemstone
Jade
A tough, prized ornamental gem that is actually two distinct minerals, jadeite and nephrite, revered for millennia in many cultures.
gemstone
Topaz
A hard, brilliant fluorosilicate gemstone occurring in many colors, from precious golden imperial topaz to popular blue topaz.
gemstone
Bog Iron
A soft, porous iron ore of limonite and goethite that forms in wetlands and bogs, historically the first iron source for many cultures.
sedimentary
Turquoise
A prized blue to blue-green copper-aluminium phosphate, often veined with dark matrix, treasured for jewelry across many cultures.
mineral
Franklinite
A black spinel-group zinc iron oxide, essentially unique to Franklin, New Jersey, where it was a key zinc and manganese ore.
mineral
Anorthoclase
A sodium-rich alkali feldspar of sodic volcanic rocks, sometimes forming large glassy crystals and the blue-flashing feldspar in larvikite.
mineral
Virgin Valley Opal
Nevada's famous precious opal, including vivid black opal and opalized wood, renowned for brilliance but a notable tendency to craze.
gemstoneMalaia Garnet
A pyrope-spessartine garnet in warm peach, salmon, and pinkish-orange tones, originally rejected by dealers and named 'malaia,' Swahili for outcast.
gemstone
Lemon Tourmaline
A bright lemon-to-canary yellow tourmaline colored by manganese, among the more cheerful and uncommon hues in the tourmaline family.
gemstone