Rock IdentifierExplore the library
Expert guides, stone profiles and a plain-English glossary — free to read.
Getting Started
Start here — the core ideas every rockhound needs.
How to Identify a Rock, Step by Step
A repeatable method: work through color, luster, hardness, streak, and shape.
Minerals, Rocks, Crystals & Gems
Four words people mix up — here's what each one actually means.
How to Photograph a Rock for the Best ID
Good light, sharp focus, scale, and a wet-vs-dry trick for better results.
Common ID Mistakes Beginners Make
The classic traps — trusting color, skipping streak, and expecting certainty.
Rock Families
How the three great rock families form and differ.
The Three Rock Families
Igneous, sedimentary, metamorphic — how each forms and how to tell them apart.
Igneous Rocks: Born of Fire
Granite to obsidian — how cooling speed and chemistry shape volcanic rock.
Sedimentary Rocks: Written in Layers
How mud, sand, and shells become stone — and why fossils live here.
Metamorphic Rocks: Changed by Force
Heat and pressure remake old rock into slate, marble, schist, and gneiss.
Fossils 101
What fossils are, how they form, and where to find them.
Properties & Tests
The diagnostic clues that unlock any identification.
The Mohs Hardness Scale Explained
The 1–10 scale, its reference minerals, and simple field scratch tests.
Luster, Streak, Cleavage & Fracture
The four properties that do the heavy lifting in identification.
Fluorescent & Radioactive Minerals
Minerals that glow under UV — and a few that need careful, safe handling.
Building a Home Testing Kit
A handful of cheap tools that let you test hardness, streak, magnetism and more.
Stone Profiles
Deep-dives on popular stones — recognize, verify, value.
The Quartz Family
The most common gem mineral — and the parent of amethyst, agate, and more.
Amethyst
Purple quartz — February's birthstone, and often heat-treated or faked.
Rose, Smoky & Citrine Quartz
Three colored quartzes — and how to tell natural citrine from heated amethyst.
Agate & Jasper
Two faces of chalcedony — one banded and translucent, one solid and opaque.
Obsidian
Natural volcanic glass — sharp, glassy, and easy to confuse with black stones.
Pyrite: Fool's Gold vs Real Gold
How to tell the shiny brass mineral from actual gold — with simple field tests.
Granite
The classic coarse, speckled igneous rock — and how to read its minerals.
Basalt
Earth's most common volcanic rock — dark, fine-grained, and often full of holes.
Marble vs Limestone
Two carbonate rocks that fizz in acid — one sedimentary, one metamorphosed.
Sandstone
Cemented sand grains — gritty, layered, and easy to identify by feel.
Opal
A water-bearing mineraloid famous for its flashing play-of-color.
Jade: Jadeite vs Nephrite
Two different minerals share the name 'jade' — plus a market full of imitations.
Turquoise
A beloved blue stone — and one of the most faked and treated in the trade.
Malachite
Vivid green copper carbonate with unmistakable banded, botryoidal patterns.
Fluorite
The rainbow mineral — cubic crystals, perfect cleavage, and often fluorescent.
Selenite & Gypsum
A very soft mineral you can scratch with a fingernail — and must keep dry.
Lapis Lazuli
An ancient deep-blue rock flecked with gold pyrite — and often imitated.
Tiger's Eye
Golden-brown quartz with a moving band of silky light (chatoyancy).
Garnet
January's birthstone — a hard, glassy group of gems in many colors.
Meteorites vs Meteor-wrongs
How to tell a genuine space rock from the many earthly impostors.
Crystals & Gems
Crystal shapes, gems, and how to spot treatments.
Crystal Systems & Habits
Why crystals grow the shapes they do — cubes, prisms, druzy, geodes and more.
Real vs Fake: Treatments & Imitations
Dyed, heated, coated, reconstituted, glass, and synthetic — how to spot them.
Collecting & Care
Find, clean, value, and care for your specimens.
How Specimens Are Valued
What drives price — and why a photo can't appraise a diamond.
Rockhounding Basics
Where to look, the law, safety, tools, and leave-no-trace ethics.
Cleaning & Caring for Specimens
Gentle methods, and which stones hate water, sun, salt, or acid.
Tumbling & Polishing Basics
How rough rock becomes glossy tumbled stones — and which stones suit it.
Displaying & Storing a Collection
Protect specimens from scratches, sunlight, dust, and lost labels.
Reading a Locality Label
Decode the cryptic labels on specimens — locality, collector, and catalog numbers.
