Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Tree Agate
A white chalcedony filled with green or black dendritic, tree-like mineral inclusions that resemble ferns or moss frozen in stone.
gemstone
Fluorite
A soft, colorful calcium fluoride mineral famous for cubic crystals, perfect octahedral cleavage, and fluorescence under UV light.
mineral
Anhydrite
A water-free calcium sulfate mineral closely related to gypsum, forming in evaporite deposits and swelling into gypsum when it absorbs water.
mineral
Aquamarine Matrix
Aquamarine crystals still attached to their natural host rock, prized as mineral specimens showing beryl in its original pocket setting.
mineral
Rutile
Rutile is a major titanium ore and the famous golden needle inclusion that gives rutilated quartz its shimmering threads.
mineral
Chrysocolla
A vivid blue-green hydrated copper silicate, soft on its own but prized as a gem when hardened by intergrown quartz or chalcedony.
mineral
Oolitic Limestone
Limestone built from tiny rounded ooid grains resembling fish roe, formed in warm, agitated shallow seas.
sedimentary
Lapis Lazuli
An intensely blue metamorphic rock of lazurite flecked with golden pyrite, prized for millennia as a gemstone and ultramarine pigment.
metamorphic
Orange Calcite
A soft, glowing orange variety of calcite colored by iron oxides, popular as tumbled stones and known for fizzing in acid.
mineral
Apache Tears
Rounded nodules of translucent obsidian, named after a Native American legend, that glow smoky brown when held to light.
igneous
Albitite
A pale rock made almost entirely of the sodium feldspar albite, formed by sodic magmatism or sodium metasomatism.
igneous
Blue Kyanite
A striking blue aluminum silicate famous for bladed crystals and anisotropic hardness that differs dramatically along and across the blade.
mineralReptile Jasper
A green-and-black mottled jasper whose scale-like patterning resembles reptile skin, often linked to Kambaba and crocodile jaspers.
mineral
Cinnamon Stone
The warm cinnamon-to-honey-brown variety of grossular garnet, also known as hessonite, with a characteristic swirly internal texture.
gemstone
Eclogite
A dense, high-pressure metamorphic rock famous for its red garnets set in bright green pyroxene, formed deep within subduction zones.
metamorphic
Perthite
An intimate intergrowth of potassium feldspar and sodium feldspar formed when a single alkali feldspar unmixes on cooling, producing fine wavy lamellae.
mineral
Ruby
The red, chromium-colored variety of corundum, prized as one of the most valuable colored gemstones and second only to diamond in hardness.
gemstone
Amphibolite
A dark, dense metamorphic rock dominated by hornblende and plagioclase, formed by medium- to high-grade metamorphism of basalt.
metamorphic
Pegmatite
An exceptionally coarse-grained igneous rock, often granitic, famous for hosting large crystals and many gemstones.
igneous
Emerald
The green chromium- and vanadium-colored variety of beryl, one of the four classic precious gemstones renowned for its rich green color.
gemstoneJet
A lightweight black organic gemstone formed from fossilized wood under pressure, a type of lignite long used in mourning jewelry.
sedimentaryWhiteschist
A rare high-pressure metamorphic schist defined by the diagnostic assemblage of talc plus kyanite, often pale and silvery.
metamorphic
Kunzite
The delicate pink-to-lilac variety of spodumene, a lithium silicate prized for soft color and strong pleochroism but tricky perfect cleavage.
gemstone
Septarian Concretion
A rounded sedimentary nodule cracked internally and filled with veins of yellow calcite, prized for its striking dragon-skin patterning.
sedimentary