Stone categories

An Overview of Stones

A photo-rich hub page for the three major rock categories—igneous, sedimentary, and metamorphic—with formation basics, scientific terminology, and direct links into Geology, Stone Science, and Natural Stones.

Explore the site by topic. Each card opens a curated hub with the best next steps.

Geology

Big-picture geology: how rocks form, how we read landscapes, and how evidence fits together.

Stone Science

Scientific terms, classification, and lab/field concepts used to describe minerals and rocks.

Natural Stones

Everyday stone types, uses, and formation—written for collectors, builders, and curious readers.

Geology Hub — Igneous

Magma and lava, cooling rates, textures, and the most common igneous rock families.

Geology Hub — Sedimentary

Weathering to lithification: layers, grains, fossils, and the structures that record environments.

Geology Hub — Metamorphic

Heat, pressure, and fluids: foliation, grade, and how rocks transform without melting.

Archaeology

Stone in human history: materials, tools, dating methods, and how context changes meaning.

Origins

Browse stones by country and region, with “known for” notes to guide collecting and sourcing.

Indigenous Peoples

Indigenous knowledge, stone use, and cultural context—approached with care, sources, and respect.

Tip: If you’re not sure where to begin, start with Geology, then open the three rock hubs (Igneous, Sedimentary, Metamorphic).

Igneous rocks

Formed by the cooling and crystallization of molten material. In scientific terms, igneous rocks are classified by texture (crystal size/arrangement) and composition (silica and mineral proportions). Common terms you’ll see: intrusive (plutonic), extrusive (volcanic), aphanitic, phaneritic, porphyritic, vesicular, glassy, and pyroclastic.

In plain terms: igneous rocks are “frozen melt.” Slow cooling underground makes bigger crystals; fast cooling at the surface makes tiny crystals or glass.

Volcanic basalt fracture texture with layered cracks

Dark basaltic rock texture with broken angular fragments

Volcanic rock surface with moss and natural pits

Pink and gray mineral-rich rock surface close-up

Close-up of lava rock fragment on a light background

Igneous links & key takeaways

Scientific classification

Learn how igneous rocks are named using QAPF (felsic–mafic mineral proportions), plus texture terms used in petrography.

Stone Science — Igneous

Field context

See igneous rocks in geologic settings—flows, intrusions, and what geologists look for in outcrops.

Geology Hub — Igneous

How geologists analyze

Connect rock evidence to processes using mapping, textures, mineral ID, and cross-cutting relationships.

Geology

Sedimentary rocks

Formed by weathering, transport, deposition, and lithification (compaction + cementation), or by chemical/biochemical precipitation. Scientific terms you’ll see: clastic, carbonate, siliciclastic, grain size (clay–silt–sand–gravel), sorting, rounding, bedding, lamination, cross-bedding, graded bedding, and diagenesis.

In plain terms: sedimentary rocks are “made from pieces” (or precipitated minerals) that get buried and glued together over time.

Rock face showing distinct sedimentary layers and a dark mineral vein

Sandstone spires and mesas in Monument Valley

Monument Valley sandstone buttes and mesas

Aerial view of eroded badlands with exposed sedimentary stratification

Badlands landscape with erosion patterns and sedimentary layers

Sedimentary links & key takeaways

Scientific naming

See how sedimentary rocks are classified by grain size, composition, and sedimentary structures.

Stone Science — Sedimentary

Outcrop interpretation

Use bedding, fossils, and structures to infer environments like rivers, deserts, beaches, and deep sea.

Geology Hub — Sedimentary

Natural-stone context

Connect sedimentary stones to common uses (building stone, tile, landscaping) and practical identification.

Natural Stones

Metamorphic rocks

Formed when existing rocks are changed by heat, pressure, and chemically active fluids—without fully melting. Scientific terms you’ll see: protolith, metamorphic facies, metamorphic grade, foliation, lineation, schistosity, gneissic banding, recrystallization, and index minerals (e.g., garnet, staurolite, kyanite, sillimanite).

In plain terms: metamorphic rocks are “re-baked and re-squeezed” rocks—minerals reorganize, new minerals can grow, and textures can align.