Gold Ore Identification: Tests, Look-Alikes and Value

You identify gold ore by finding a yellow metal that is soft, heavy and leaves a golden-yellow streak, inside a rock that usually looks like white quartz. The U.S. Geological Survey gives the two tests that settle most cases: poke the metal with a steel point, and real gold gouges or dents like soft lead, while its look-alikes flake, powder or crumble; and scrape it on unglazed porcelain, where gold leaves a golden-yellow streak, pyrite and chalcopyrite a dark green to black streak, and common micas a white one.

Most ore does not show any gold at all, so a rock with no visible gold can still be ore. Only an assay tells you how much it holds.

Gold is found in volcanic, sedimentary, metamorphic and granitic rocks, according to the USGS booklet on prospecting for gold. In practice a few settings account for most finds:

• Quartz veins. The mining-equipment guides that rank for this search all put quartz veins first, often in greenstone (altered basalt) or schist. Geology In describes gold-bearing veins as quartz with pyrite, chalcopyrite, galena or arsenopyrite, formed 3 to 10 km down at 200 to 400 °C.
• Iron-stained quartz. Geology In says to look for quartz outcrops with iron-stained surfaces, a sign that sulfides were there and have rusted.
• Sulfide-rich rock. Geology.com notes that gold and pyrite form under similar conditions and some pyrite carries 0.25% gold by weight or more, locked inside the crystals.
• Stream gravels. The USGS explains that placer gold eroded from veins collects in streams, often on or near bedrock, with black sands that are mostly magnetite.
• Limestone and silty carbonate rock in Nevada. Carlin-type deposits hold gold that is invisible, microscopic or dissolved in arsenic-rich pyrite, and can only be found by chemical analysis (Wikipedia).

Visible gold in ore appears as bright yellow flecks, streaks, threads or small nuggets set in white or translucent quartz, according to Geology In, which also stresses that visible gold is not common. Geology.com adds that natural gold is golden yellow and turns paler when it is naturally alloyed with silver, keeps its metallic shine without tarnishing, and in stream gravels shows uniform colour and rounded edges.

What you usually see instead is the company gold keeps: brassy pyrite cubes, rusty brown pits where sulfides have weathered out, and bleached or altered rock around the vein. Those are clues to test, not proof of gold.

None of these needs a lab. Do them in this order, because the first two settle most specimens.

• Pin test. Press a steel pin or needle into the grain. Gold dents or bends; pyrite is brittle and thin pieces break, and mica flakes apart (Geology.com; USGS).
• Streak test. Rub it on the back of an unglazed tile. Golden yellow means gold; greenish black means pyrite or chalcopyrite; white means mica (USGS).
• Hardness. Gold is only 2.5 to 3 on the Mohs scale, so a copper coin or steel point marks it. Pyrite, at 6 to 6.5, scratches copper; chalcopyrite sits at 3.5 to 4 (Geology.com). See our Mohs hardness scale guide.
• Shape and striations. Pyrite forms cubes, octahedra or pyritohedra with fine parallel lines on the faces; gold particles have rounded edges and no striations (Geology.com).
• Weight in the pan. Pure gold has a specific gravity of 19.3 and natural gold 16 to 18, against about 2.5 for ordinary rock (USGS), so gold stays at the bottom of a pan when everything else washes out. Pyrite is only about 5 (Geology.com).

Acid and home chemistry kits sold for jewellery are not listed as field methods by the USGS or Geology.com; the mining guides that mention aqua regia describe it as a laboratory step.

The USGS names three minerals as fool's gold: pyrite, the commonest, chalcopyrite and weathered mica. The ranking mining guides add two more worth ruling out.

• [Pyrite](/lookup/rocks-and-minerals/pyrite). Brassy, hard (6 to 6.5), brittle, greenish-black streak, often in striated cubes.
• Chalcopyrite. Softer than pyrite (3.5 to 4) but still brittle, with a greenish-black streak (Geology.com; USGS); the JXSC guide adds that it oxidises green or black.
• Weathered mica. Flakes of biotite or phlogopite flash gold in a pan, but break under a pin and leave a white streak (Geology.com; USGS). Muscovite flakes the same way.
• Jarosite. A yellow-brown mineral of oxidised deposits, hardness 2.5 to 3.5, pale yellow-brown streak and much lighter than gold (JXSC mining guide).
• Native copper. Reddish, with a copper-red streak, and it turns green as it oxidises (JXSC mining guide).

Gold is sold by the troy ounce, which is exactly 31.1034768 grams (Wikipedia, Troy weight). At the USGS figure of 19.3 for pure gold, one troy ounce fills about 1.6 cubic centimetres, a cube roughly 1.2 cm (under half an inch) on each side. Natural gold is less dense, 16 to 18 according to the USGS, so an ounce of nuggets takes up about 1.7 to 1.9 cubic centimetres. These are our own calculations from those two sourced figures.

Prices, dated:

• Spot gold: US$4,294.74 per troy ounce on 25 September 2026 (Trading Economics). That works out to about US$138 per gram of pure gold.
• Natural gold contains silver and other metals, and Geology.com notes the specific gravity falls as gold alloys naturally with silver or copper, so a nugget is worth less than its weight in pure gold.
• Ore: a Turquoise Ridge ore sample shown on Wikipedia's Carlin-type page grades about 0.35 ounces of gold per ton. At the spot price above, that is roughly US$1,503 of gold in a ton of rock before any mining or processing cost, and about 0.012 grams, or US$1.66, in a 1 kg hand specimen (our calculation, using the US short ton of 2,000 pounds).

That last line is the honest answer to whether a gold-looking rock is valuable: ore is valuable in thousands of tons, rarely as a single rock, unless the gold is visible in quantity.

The ranking guides sort ore into types. In plain terms:

• Quartz vein ore: gold in milky white or smoky grey quartz, often with sulfides; the classic prospector's target.
• Sulfide ore: gold locked inside pyrite, arsenopyrite or chalcopyrite; it rarely shows any visible gold.
• Electrum: a natural gold-silver alloy, paler than gold.
• Iron oxide copper-gold ore: magnetite or hematite rock with chalcopyrite; the JXSC guide uses a magnet to detect the magnetite, not the gold. Cementl gives gold grades of 0.1 to 3 grams per tonne for this type.
• Epithermal ore: formed 1 to 2 km below the surface at 150 to 300 °C near volcanoes (Cementl).
• Placer gold: loose grains and nuggets in stream gravels (USGS).

For a collector, the practical split is visible gold (test it with the five checks above) versus invisible gold (only an assay will find it).

Fire assay is the standard laboratory method for gold. A caution from the sources we opened:

• Labs differ in quality. The mining journal ICMJ reports a Bureau of Land Management test of 65 North American laboratories that found serious inconsistencies, including false precious-metal readings on blank samples and valuable samples reported as having none. Prices in that study ran from US$60 for a fire assay to US$2,250 for another method, and the cheapest was not always the least accurate. Ask a lab for its track record before you send samples.

On public land, the BLM allows collecting reasonable amounts of rocks and minerals for non-commercial use, but not in areas with active mining claims or where mineral rights are privately owned; check with the local field office first.

Take two photos in daylight: the whole rock with a coin for scale, and a close-up of the yellow grains that fills the frame. If you did a streak test, add a photo of the streak next to the rock. RockLens suggests a likely identification from the photo, and flags pyrite and mica look-alikes. Then confirm with the pin and streak tests above; a photo cannot measure softness or weight, and it cannot find invisible gold.

Research and drafting used AI assistance, and every statement was checked against the sources listed below. Tests and look-alikes come from the U.S. Geological Survey and Geology.com; ore settings from the USGS, Geology In and the mining guides from JXSC, Xinhai and Cementl; invisible gold from Wikipedia; assay cautions from ICMJ. The gold price is the Trading Economics spot price for 25 September 2026. Volume and ore-value figures are our own arithmetic from those numbers.