Mineral identification key
Answer as many questions as you can. Every answer is optional, and the list narrows as you go. If you reach zero matches, it tells you which answer caused the conflict — that is usually a weathered surface giving a false reading, not a rare mineral.
1.How hard is it?
optionalThe single most useful test. Try to scratch a fresh surface — not a weathered crust — and rub the powder away to check the mark is real.
2.What does the surface look like?
optionalJudge lustre on a freshly broken face in good light. Tarnish and weathering will mislead you.
3.What colour is the streak?
optionalDrag the specimen firmly across the unglazed back of a ceramic tile. The powder colour is often nothing like the specimen colour — that is exactly why this test is worth doing.
4.How does it break?
optionalLook at a broken edge under a bright light and turn it slowly. Flat faces that flash all at once are cleavage; curved shiny surfaces are fracture.
5.Any of these true?
optionalPick every one that applies. These are the shortcuts — a magnet sticking to a rock narrows the whole list down to one.
Safety: never taste a mineral you have not already narrowed to halite, never crush fibrous green material, and wash your hands after handling anything metallic and heavy.
6.What colour is it?
optionalDeliberately last, and it never rules anything out — it only reorders the list. Colour is the least reliable property in mineralogy.
- ApatiteH 5 · Often a distinctive sea-green or blue-green; also yellow and violet
- Augite (Pyroxene)H 5.5–6 · Dark green-black to brown-black; typically duller than hornblende
- AzuriteH 3.5–4 · A deep azure blue that darkens almost to black in massive material
- BariteH 3–3.5 · Usually white or pale; sand-included 'barite roses' are reddish brown
- Beryl (Emerald & Aquamarine)H 7.5–8 · Green beryl is emerald
- BiotiteH 2.5–3 · Dark brown to black
- CalciteH 3 · Usually white or colourless
- CassiteriteH 6–7 · Usually near black or dark reddish brown
- Chalcedony (Agate, Jasper, Chert)H 6.5–7 · Any colour
- ChalcopyriteH 3.5–4 · Deeper
- ChloriteH 2–2.5 · Almost always a distinct green
- ChromiteH 5.5 · Brownish black
- CopperH 2.5–3 · Fresh surfaces are bright copper-red; exposed surfaces tarnish brown
- Corundum (Ruby & Sapphire)H 9 · Red corundum is ruby; every other colour is sapphire
- DolomiteH 3.5–4 · Typically white to pale pink or buff
- EpidoteH 6–7 · A very particular yellow-green often described as pistachio green
- Feldspar (Orthoclase & Plagioclase)H 6–6.5 · Salmon pink and creamy white are the classic colours
- FluoriteH 4 · Famous for colour zoning — a single crystal can be purple at the corners and green in the middle
- GalenaH 2.5–2.75 · Bright silvery lead-gray when fresh
- GarnetH 6.5–7.5 · Deep brownish red is by far the most common
- GoethiteH 5–5.5 · Yellow-brown to near black
- GoldH 2.5–3 · Always a rich buttery yellow
- GraphiteH 1–2 · Steel gray to black with a slightly greasy sheen
- GypsumH 2 · Usually colourless or white; sand inclusions give desert roses their brown colour