PyriteMohs 6-6.5
Brassy yellow, metallic luster, often cubic or pyritohedral crystals with striated faces. Greenish-black streak distinguishes from gold (yellow streak).
Photo: Wikipedia contributors · wikipedia
Mineral Identifier
Minerals get identified by a short list of physical properties: hardness, streak color, luster, cleavage, and crystal habit. This identifier reads what's visible from a photo — color, luster, habit — and then names the one diagnostic test that separates each candidate from its closest lookalike. The result is a ranked candidate list with the next step written into each card.
- Returns Mohs hardness range per match
- Calls out luster, cleavage, and habit
- Names the streak / acid / magnet test to confirm
- Covers rockhounding and common ore minerals
Reviewed by RockHoundR Field Team · Field identification & geology editors · Last verified
Quick answer
Photograph a single mineral specimen on a plain background. The identifier returns three ranked matches with Mohs hardness, luster, and one diagnostic field test (streak, acid, magnet, hardness scratch) to separate each candidate from its closest lookalike.
A mineral is a naturally-occurring inorganic substance with a fixed chemical composition and crystal structure. Common rockhounding minerals — quartz, calcite, pyrite, galena, hematite, magnetite, mica — each have a property fingerprint that separates them. The identifier reads color, luster, and habit from the photo, then writes the one test (streak, acid, magnet, hardness) that confirms or rules out each candidate.
Luster is the single most underused field test. Metallic luster narrows the field to about a dozen common minerals: pyrite, galena, magnetite, hematite (specular form), chalcopyrite, sphalerite, and a few others. Submetallic narrows it further. Vitreous opens onto quartz, calcite, fluorite, feldspar. Resinous points at sphalerite or sulphur. Reading luster from a photo is the strongest single ID move after habit.
Streak — the color a mineral leaves when scraped on unglazed porcelain — separates hematite (red-brown streak) from magnetite (black), pyrite (greenish-black) from chalcopyrite (black), and many color-overlapping minerals. The identifier names which streak result you should look for, but you'll need a streak plate to confirm.
Visual identification guide for common minerals
These six show up most often in mineral ID submissions. Each card shows a reference specimen and the test that confirms it.
GalenaMohs 2.5
Lead-gray metallic cubes with three cleavages at right angles. Very dense — feels much heavier than its size. Mohs 2.5 (knife scratches).
Photo: Wikipedia contributors · wikipedia
CalciteMohs 3
Rhombohedral cleavage in three directions, vitreous luster, fizzes vigorously in dilute hydrochloric acid. Mohs 3 (copper penny scratches).
Photo: Wikipedia contributors · wikipedia
MuscoviteMohs 2.5-3
Splits into thin transparent sheets along basal cleavage. Pearly luster on cleaved surfaces. Mohs 2–2.5.
Photo: Wikipedia contributors · wikipedia
HematiteMohs 5.5-6.5
Reniform 'kidney ore' or metallic-specular varieties. Red-brown streak is diagnostic, even when the specimen looks black.
Photo: Wikipedia contributors · wikipedia
MagnetiteMohs 5.5-6.5
Black metallic octahedral crystals. Strongly magnetic — sticks to a magnet directly. Black streak (vs hematite's red-brown).
Photo: Wikipedia contributors · wikipedia
Mineral property comparison
Six common minerals side by side. Streak and acid reaction settle most lookalike confusions instantly.
| Specimen | Hardness (Mohs) | Streak | Luster | Cleavage | Field tell |
|---|---|---|---|---|---|
| Pyrite | 6-6.5 | greenish-black to brownish-black | metallic | indistinct | Greenish-black streak; striated cubes; brassy. |
| Galena | 2.5 | lead-gray | metallic | perfect cubic | Cubic cleavage, very dense, lead-gray streak. |
| Calcite | 3 | white | vitreous | perfect in 3 directions | Fizzes in dilute HCl; rhombohedral cleavage. |
| Muscovite | 2.5-3 | white | pearly | perfect basal | Splits into thin transparent sheets. |
| Hematite | 5.5-6.5 | cherry-red to reddish-brown | metallic to earthy | none | Red-brown streak even when specimen looks black. |
| Magnetite | 5.5-6.5 | black | metallic | none | Strongly magnetic; black streak; octahedral. |
Identify by luster
Luster narrows the candidate list further than color does. Read it first.
- Metallic
- Pyrite, galena, magnetite, hematite (specular), chalcopyrite, sphalerite, marcasite.
- Submetallic
- Hematite (massive), goethite, cuprite, ilmenite.
- Vitreous (glassy)
- Quartz, calcite, fluorite, feldspar, topaz, beryl.
- Pearly
- Mica (muscovite, biotite), talc, gypsum (selenite variety).
- Resinous / waxy
- Sphalerite, sulphur, opal, amber.
- Earthy / dull
- Limonite, kaolinite, weathered hematite, weathered pyrite (limonite pseudomorph).
Identify by streak
Streak is the color of the powdered mineral on unglazed porcelain. Often the deciding test when luster and color are similar.
- Red-brown
- Hematite. Diagnostic even when specimen looks black or metallic.
- Black
- Magnetite, ilmenite, pyrolusite, biotite.
- Greenish-black
- Pyrite (separates from gold, which streaks yellow).
- Yellow-brown
- Limonite, goethite.
- White
- Most non-metallic minerals — quartz, calcite, feldspar, fluorite, gypsum.
- Brown-black
- Sphalerite (despite the variable specimen color).
How the mineral identifier works
- Step 1
Photograph the mineral
Show a fresh face and the overall habit. Natural light reads true color and luster best.
- Step 2
Add locality if you know it
Mine name, district, or rock unit. Locality narrows possibilities sharply in ore districts.
- Step 3
Get 3 ranked matches with a test
Each result: mineral name, Mohs hardness and luster, plus one field test (streak, acid, magnet) to confirm.
Take a photo that identifies well
- Capture a fresh broken surface — weathered faces hide diagnostic features.
- Include a scale (coin, hand) for size reference.
- Show luster — a slight angle helps separate metallic vs vitreous vs dull.
- Photograph both a flat face and an angled face for cleavage.
What to avoid
- Heavily weathered or coated specimens.
- Backlit shots — luster disappears.
- Cropping out the crystal habit.
- Polished slabs where original surface is gone.
How accurate is this mineral identifier?
Photos read color, luster, and habit well. Streak, acid reaction, hardness, density, and magnetism — the actual diagnostic tests — they don't show.
Strong on
- Common metallic-luster minerals: pyrite, galena, magnetite, specular hematite.
- Distinctive habits: cubic galena, rhombohedral calcite, sheet mica, botryoidal hematite.
- Color-plus-habit combinations that narrow the field hard (yellow-brassy-cubic → pyrite).
Less reliable on
- Massive specimens without crystal form — many ore minerals look identical.
- Weathered surfaces — original luster and color are obscured.
- Color-only identifications — too many minerals share each color band.
- Anything where streak, acid reaction, or specific gravity would decide it.
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Mineral Identifier FAQ
What's the difference between a mineral and a rock identifier?
A mineral is a single chemical substance with a defined crystal structure (quartz, calcite, pyrite, galena). A rock is typically an aggregate of multiple minerals (granite is quartz + feldspar + mica; basalt is plagioclase + pyroxene). This tool focuses on single-mineral specimens. For an aggregate, use the rock identifier instead — the prompts and lookalike lists differ.
Can it identify ore minerals?
Yes. Common sulfides (pyrite, galena, sphalerite, chalcopyrite), oxides (hematite, magnetite, cassiterite), carbonates (smithsonite, malachite, azurite), and a handful of phosphates and sulphates are covered. Industrial ores and rare-earth-bearing minerals are weaker because they often look identical to the eye without lab work.
Will it tell me which streak test to run?
Yes — when useful. The identifier flags lookalikes that share color but have different streak (hematite is red-brown; magnetite is black) and explicitly suggests the streak as the diagnostic test in each card. You'll need a piece of unglazed porcelain (the back of a tile works) to actually run it.
Does it work for fluorescent or radioactive minerals?
Photos can't show fluorescence or radioactivity directly. The identifier can name a specimen and note that it commonly fluoresces (fluorite, calcite, willemite, scheelite) but a UV lamp or Geiger counter is needed to confirm. Treat the result as a prompt to run the test, not a substitute.
Why does it ask about locality?
Mineralogy is geography. The same green-colored mineral could be malachite at one mine and dioptase at another. Adding the mine, district, or country narrows the answer significantly — but it's never required, and we never invent details about the location.
How is this different from the crystal identifier?
The crystal identifier is tuned for well-formed crystals with visible faces and termination — it leads with habit and prefers varietal names (amethyst, citrine). The mineral identifier handles massive, granular, fibrous, or botryoidal specimens with no clear crystal shape — it leads with luster and streak. Pick the one that matches what you're holding.
References & sources
Property data and reference imagery used on this page are cross-checked against the following sources.
- Mindat.org — mineral properties
Primary reference for streak, luster, cleavage, and locality data used in the comparison table.
- USGS Mineral Resources Online Spatial Data
Federal source for U.S. mineral occurrences and ore districts.
- Smithsonian Mineral Sciences
Reference imagery and species pages for the visual identification guide.