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How to identify rocks and minerals

How do you identify rocks and minerals? Colour, hardness, lustre and streak point the way. This guide explains the simple tests, and orecast shows which raw materials are on record at your site.

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Gesteine & Mineralien bestimmen
Foto: JJ Harrison (https://www.jjharrison.com.au/) (Wikimedia Commons), CC BY-SA 4.0

Minerals are identified through a few properties. You test hardness with the Mohs scale by scratching what is harder or softer. The streak on a rough porcelain plate shows the true powder colour, which often differs from the surface. Add lustre, cleavage and crystal form. For rocks it matters whether they are made of grains, crystals or layers and how they formed. orecast adds to this by showing the documented raw materials and the local geology at your location. That way you know what actually occurs in the area before you guess.

A few classic mix-ups dissolve with simple means. Pyrite gleams gold but is brittle and leaves a greenish-black streak, while real gold is soft and bends. Calcite and quartz often look alike; calcite scratches easily with a pocket knife and fizzes in dilute acid, quartz shrugs both off. Always work on a fresh face. Weathered crusts fake colours and lustre that have little to do with the interior, and one well-placed hammer blow settles more than long guessing.

A small field kit covers most situations: a ten power loupe, a pocket knife, a piece of unglazed porcelain, a magnet and a dropper bottle of dilute acid for the carbonate test. Just as useful is thinking in exclusions. In granite country nobody needs to ponder volcanic glass, and checking beforehand which rocks and raw materials a region carries cuts hundreds of options down to a handful. Colour alone remains the worst guide, since most minerals occur in several colours.

Real material trains the eye best. Geological collections at museums and universities display labelled regional pieces, and mineral shows let you compare specimens in hand. Many European geoparks run guided walks where geologists explain rocks right at the outcrop. Building a small reference collection of common minerals lets you test new finds against known pieces rather than against photos. That is how professionals learned it too.

Common minerals and rocks at a glance

A quick visual key to the stones you will handle most often, and how to tell them apart.

Fossil: Quartz
QuartzQuartz is the most common mineral in the Earth's crust and turns up glass-clear as rock crystal, milky, or violet as amethyst. You recognise it by hardness: it scratches glass and steel with ease, yet has no cleavage and breaks with a curved, shell-like fracture. Look for it in veins, on spoil heaps and in almost any gravel bed.
Fossil: Feldspar
FeldsparFeldspars make up the bulk of many rocks and usually look white, grey or flesh-pink. Unlike quartz they split along smooth, stair-stepped flat faces that catch the light. You meet them most often as the pale grains in granite.
Fossil: Mica
MicaMica is easy to spot: it glitters silvery or dark brown and peels into wafer-thin, flexible flakes. Pale muscovite and dark biotite are the common ones. They sit in granite and gneiss and flash out of the rock along many road cuts.
Fossil: Pyrite
PyritePyrite is the classic fool's gold: brass-yellow with a metallic shine, often in surprisingly perfect cubes. It gives itself away against real gold by its hardness and its greenish-black streak, and it is brittle rather than soft. Look for it in ore veins, in shale and on mining dumps.
Fossil: Calcite
CalciteCalcite is soft, usually colourless to white, and splits into slanted rhombs that look like squashed cubes. The sure test is a drop of dilute acid: calcite fizzes clearly while quartz stays quiet. It fills veins, builds limestone and hangs in caves as dripstone.
Fossil: Fluorite
FluoriteFluorite stands out through its colours, from green and violet to blue and yellow, often in clear cubes. It is much softer than quartz and cleaves at the corners into little octahedra. On the dumps of the Harz, Erzgebirge and Black Forest it is a common and popular find.
Fossil: Granite (rock)
Granite (rock)Granite is the textbook plutonic rock: a coarse-grained mix of pale quartz, pink or white feldspar and dark mica. It formed deep underground from slowly cooling melt. It crops out over wide areas in ranges like the Bavarian Forest, the Fichtel Mountains and the Harz.
Fossil: Basalt (rock)
Basalt (rock)Basalt is a dark, fine-grained volcanic rock that often freezes into five- or six-sided columns. It is heavy, hard and mostly black to grey. In the Eifel, the Vogelsberg and the Kaiserstuhl it lies exposed in old quarries and lava flows.

Images generated with AI.

38documented mineral & ore points
138fossil sites
636historical sites
☢️ 64 sites within 50 km are flagged as war or WWII sites with possible unexploded ordnance. Never dig there, it is a danger to life.

Documented finds nearby

Fossil sites nearby

Collecting, law & safety

A promising geology is never a guarantee, and you will not find invented numbers here. Collecting and digging are regulated across Europe and usually need a permit. Protected sites, nature reserves and disused mines are off-limits and can be deadly.

Useful gearAd
🔍 10× loupeReveals crystal faces and fossil detail the bare eye misses. It helps the app's photo ID too.🔦 UV torch (365 nm)Amber glows under UV and many minerals fluoresce. That is the one trick that really works on a night beach.🗃️ Compartment boxSo the best find of the day does not crumble in a jacket pocket.

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Frequently asked questions

How do I test a mineral's hardness?

With the Mohs scale from 1 to 10. A fingernail scratches to about hardness 2, a copper coin to 3, a pocket knife to around 5. What the knife cannot scratch is harder.

What is the streak test?

You drag the mineral across an unglazed porcelain plate. The colour of the powder streak is often more telling than the surface colour and helps separate similar minerals.

How do I tell a rock from a mineral?

A mineral is a uniform substance with a fixed composition, a rock is a mixture of several minerals. Granite, for example, is quartz, feldspar and mica.

More guides:
Gold & ore in the Harz · Silver & minerals in the Ore Mountains · Fossils of the Swabian Alb · Gold & minerals in the Black Forest · Volcanoes & geology of the Eifel · Fossils in Solnhofen & the Altmühl valley · Gold panning in the Alps & Austria · Fossils in the Ruhr area · Finding amber on the Baltic coast · Agate & gemstones in Idar-Oberstein · Find fossils near me · Gold panning near me · Rockhounding near me · How to identify fossils · Collecting fossils and minerals: allowed or not?