How to Identify Pyrite
Pyrite — iron sulfide, the original 'fool's gold' — is the most misidentified mineral there is. The good news: two quick tests (streak and hardness) reliably separate it from real gold, which is soft and leaves a yellow streak.
Quick Facts
- hardness
- 6–6.5 (scratches glass)
- streak
- Greenish-black to brownish-black
- luster
- Metallic
- color
- Pale brass-yellow, often with a golden tarnish
- crystal System
- Isometric (cubes, pyritohedrons, octahedra)
- cleavage
- None / indistinct — conchoidal to uneven fracture
- specific Gravity
- 4.9–5.2 (heavy, but far lighter than gold's 19.3)
Where to Find It
Pyrite is extremely widespread. It forms in hydrothermal veins, in sedimentary rocks like shale and coal, in metamorphic rocks, and alongside other sulfide ores. Look for glinting brass-colored cubes in shale and slate, in quartz veins, in coal seams, and on mine dumps. Well-formed cubic crystals are a collector favorite from localities such as Spain and Peru.
What Pyrite Looks Like
- A pale, brassy metallic yellow — cooler and paler than the rich buttery yellow of real gold.
- Sharp geometric crystals: cubes (often with striated faces), twelve-sided pyritohedrons, and octahedra.
- Striations — fine parallel grooves — running across crystal faces, and set at right angles on adjacent cube faces.
- A bright metallic luster that can tarnish to a darker golden or iridescent film.
- Brittle behavior: it shatters or crumbles when struck, rather than denting or bending.
- Often occurs as cubes embedded in gray shale or slate, or as masses in quartz veins.
Simple Tests to Confirm It’s Pyrite
You can do these at home with basic tools. They won’t damage a good specimen.
Streak test (the decisive one)
Drag the specimen across unglazed porcelain. Pyrite leaves a greenish-black to brownish-black streak. Real gold leaves a shiny yellow streak. This single test reliably separates fool's gold from the real thing — a dark streak means pyrite, not gold.
Hardness test
Pyrite is hard (6–6.5): it scratches glass and a steel knife will not scratch it. Gold is soft (2.5–3) and a knife cuts it easily. So if your 'gold' scratches glass and resists a knife, it is pyrite; if it is soft enough to nick with a pin, it may actually be gold (or a soft imitation).
Crystal-form and striation check
Look for cubes and other sharp geometric crystals with striated faces. Gold essentially never forms neat cubes — it occurs as nuggets, flakes, and dendritic wires. Sharp brass-colored cubes with grooved faces are a pyrite fingerprint.
Heft / specific-gravity comparison
Pyrite is dense (SG ~5) but gold is astonishingly heavier (SG ~19.3 — nearly four times as dense). A gold nugget feels shockingly heavy for its size; pyrite feels merely 'metal-heavy.' If a small piece feels almost unbelievably heavy, be surprised — pyrite never does that.
Not sure if your specimen is Pyrite?
Get an AI-powered first guess from a photo, then use the tests above to confirm.
Look-Alikes & How to Tell the Difference
Gold (native gold)
The classic confusion. Gold is soft (a knife or pin marks it), malleable (dents rather than shatters), leaves a yellow streak, is far denser, and never forms cubic crystals. Pyrite is hard, brittle, leaves a black-green streak, and forms cubes. The streak test alone usually settles it.
Chalcopyrite
Another brassy sulfide, but softer (3.5–4, so a knife scratches it), often with an iridescent purple-blue tarnish, and it does not form good cubes. Its streak is also greenish-black. Use hardness: pyrite resists a knife, chalcopyrite does not.
Marcasite
Same chemistry as pyrite (FeS2) but a different crystal structure — paler, more tabular or spear-shaped 'cockscomb' crystals, and it is more prone to crumbling and oxidizing. Marcasite tends to be paler and forms radiating or tabular groups rather than clean cubes.
Mica (biotite/phlogopite flakes)
Golden mica flakes glinting in rock fool people from a distance, but mica is very soft (2–3), peels into thin flexible sheets, and is not metallic up close. Pyrite is hard, brittle, and truly metallic. If it flakes into sheets, it is mica, not pyrite or gold.
Frequently Asked Questions
How do I tell pyrite from real gold?+
Run the streak test: rub it on unglazed porcelain. Pyrite leaves a greenish-black or brownish-black streak; gold leaves a yellow one. Back that up with hardness — pyrite is hard and brittle and scratches glass, while gold is soft and malleable and a knife marks it. Pyrite also forms cubes and is far lighter than gold. Between streak and hardness, fool's gold is easy to unmask.
Why is pyrite called fool's gold?+
Because its brassy yellow color and metallic shine have fooled prospectors and hopeful finders for centuries into thinking they struck gold. The resemblance is only skin-deep: pyrite is iron sulfide, hard and brittle, while gold is a soft, heavy, unreactive metal. Simple tests separate them instantly, but the visual similarity keeps the nickname alive.
Is pyrite worth anything?+
As a mineral, pyrite is common and inexpensive, though well-formed cube clusters from famous localities are collectible. It has industrial history as a sulfur source and is a minor gold-ore associate (real gold sometimes hides within pyrite-rich deposits). But a lump of ordinary fool's gold has little monetary value — its worth is mostly educational and aesthetic.
Does pyrite rust or break down?+
Yes. Pyrite can oxidize over time — especially in humid conditions — producing iron oxides and sulfuric acid, a process sometimes called 'pyrite disease' that crumbles specimens and can damage nearby minerals or storage. Keep collectible pyrite dry and stable, and be aware that oxidizing pyrite in rock can stain and weaken it.
Can a photo app identify pyrite?+
A photo app can recognize pyrite's brassy color and cubic crystals and is genuinely useful for flagging 'this is probably pyrite, not gold.' But because color alone drives the classic gold confusion, confirm with the streak and hardness tests — a black-green streak and glass-scratching hardness prove pyrite in seconds where a photo can only suggest it.
Related identification guides
This field guide is educational. Visual identification and simple at-home tests are helpful first steps, but they are not a certified geological, gemological, or meteorite analysis. Verify valuable, hazardous, or scientifically important finds with a qualified expert.