Pyrite vs. Gold: 5 Tests That Expose Fool's Gold

Entire ships were once loaded with it. In 1577, Martin Frobisher hauled hundreds of tons of glittering ore back to England from the Canadian Arctic; it turned out to be worth less than the voyage's biscuits. Pyrite — iron sulfide, "fool's gold" — has been humbling optimists for centuries. The consolation: telling them apart takes five minutes and no equipment more exotic than a bathroom tile.

Know your suspect

Pyrite (FeS₂) is a brassy, metallic mineral that loves geometry — cubes, striated faces, twelve-sided crystals. Gold (Au) is a native metal: soft, dense beyond anything else in the pan, and utterly indifferent to forming pretty crystals in nature.

They genuinely do look alike at a glance, especially as small grains in gravel. Every test below exploits a way in which they are, physically, almost opposites.

Test 1: The streak

The classic, and the closest thing to a verdict. Drag the specimen across unglazed porcelain (the back of a ceramic tile):

• Gold streaks golden yellow — the powder is the same color as the metal.
• Pyrite streaks greenish-black to brownish-black — the brassy color vanishes entirely.

One firm stroke, one look, done. This is the same streak logic that anchors the whole identification method.

Test 2: Hardness — the pin test

• Gold is soft: 2.5–3 on the Mohs scale. A steel pin or knife point digs in and leaves a shiny dent or gouge. You can literally carve gold.
• Pyrite is hard: 6–6.5. A knife point skates off or, with force, chips off brittle fragments. Pyrite refuses to dent.

Flip it around: pyrite can scratch glass; gold never can.

Test 3: Malleability — dent or crumble

Put a grain on a hard surface and press it with a pin or tap it with a hammer:

• Gold flattens. It's famously malleable — it deforms like stiff clay and stays in one gleaming piece.
• Pyrite shatters. It's brittle; pressure produces dark crumbs and dust, not a flake.

For pan concentrates this is the prospector's favorite: real colors squash under a needle; fool's gold pops and fragments.

Test 4: The sun test

Take it outside and rotate it in direct light:

• Pyrite glitters. Its flat crystal faces flash like signal mirrors — bright, twinkling, angle-dependent sparkle.
• Gold glows. A soft, even, buttery luster that barely changes as you turn it, and stays rich-looking even in shade.

In a gold pan, pyrite winks at you as the water swirls; gold sits fat and constant at the bottom of the swirl. Which brings up —

Test 5: Heft and behavior in the pan

Gold's density is 19.3 g/cm³ — nearly four times pyrite's 5.0, heavier than lead. Even tiny amounts feel improbably heavy:

• In a pan, gold stays put at the bottom through swirl after swirl; pyrite grains dance and wash away with the black sand.
• A gold nugget of any size feels like a small miracle in the hand; a same-sized pyrite chunk feels like a rock.

Density is also why gold concentrates in stream gravels behind boulders and in crevices — physics has been panning for you for millennia.

The scorecard

Test	Gold	Pyrite
Streak on porcelain	Golden yellow	Greenish-black
Knife point	Dents, gouges	Skates or chips
Under pressure	Flattens	Crumbles
In sunlight	Even glow	Glittery flashes
Density	19.3 — extreme	5.0 — ordinary-heavy
Crystal shape	None (nuggets, flakes, wires)	Cubes, striated faces
Tarnish	Never	Dulls, browns with age

One caution: a third mineral, chalcopyrite, plays the same trick with a more yellow tone and often a peacock-blue tarnish; it fails the same tests pyrite fails. And gold-colored mica flakes — the glitter in every creek — are so light they float on a breath, which no metal does.

If it passes every test

Don't sell, melt, or ship anything yet. Weigh it, photograph it, note the location, and get a second opinion from a local assayer, jeweler with XRF equipment, or gold prospecting club — most clubs will confirm a find for the price of showing it off. Real gold in your pan usually starts as specks, not nuggets, and specks that pass the streak, squash, and stay-put tests are the real thing.

And if it crumbled greenish-black on the tile — congratulations anyway. You now know exactly how not to buy a shipload of it.