Gold
Au · Cubic · also called native gold, placer gold
Native gold is soft, heavy, and unreactive. Those three properties settle almost every 'is this gold?' question in under a minute, which is fortunate, because far more people find pyrite, chalcopyrite, and weathered mica than ever find gold. In stream gravels gold turns up as flattened flakes and rounded grains rather than sharp crystals — running water hammers it flat.
Properties
- Mohs hardness
- 2.5–3
- Streak
- golden
- Lustre
- metallic
- Colour
- Always a rich buttery yellow, and the colour does not change with the angle you hold it at. Gold never tarnishes, so a weathered nugget looks the same as a fresh one.
- Cleavage
- No cleavage. Gold deforms rather than breaks.
- Fracture
- Hackly (jagged), but it bends and dents long before it tears
- Specific gravity
- 15–19.3 (water = 1)
- Magnetism
- Not magnetic
- Acid test
- No reaction
- UV
- Not fluorescent
Tests that confirm gold
- Malleable: a genuine flake flattens under a knife point instead of shattering into powder.
- Extremely heavy. A pea-sized piece feels absurd in the hand — roughly seven times heavier than a same-size quartz pebble.
- Streak is golden yellow, never black or green.
What gold gets confused with
Each of these is settled by one test. Run that test first.
Pyrite is brittle and hard (6–6.5) — it crushes to a dark green-black powder under a knife. Gold is soft (2.5–3) and smears into a bright yellow smudge.
Chalcopyrite is a brassier, greener yellow and usually shows an iridescent purple-blue tarnish. Its streak is greenish black.
Mica flakes float or drift in water and peel into elastic sheets. Gold sinks instantly and cannot be peeled.
Where it is found
Quartz veins in older mountain belts, and the heavy fraction of stream gravel downstream of those veins. In the field it concentrates behind boulders, on the inside of bends, and at the base of gravel bars where current slows.
Is it worth anything?
Gold is worth real money by weight, but the flakes most people recover from a pan amount to a few dollars. Specimen gold still attached to quartz is often worth considerably more than its melt value to collectors.