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Rock Identification Chart: Match Your Find in 5 Steps

October 1, 2026 / 9 min read / RockhoundID Team

Most rock charts online are one big image: tiny photos, bright colors and no hint of which columns actually matter. This one is a real table you can read on your phone at the creek, with the test that settles each match.

How do you use a rock identification chart in 5 steps?

You need a steel nail, a copper coin, a piece of glass, the unglazed back of a white bathroom tile, a fridge magnet and a drop of vinegar. Then work down this list.

1. Find a fresh surface. Scrub off dirt and look at a clean, ideally broken face. If you see grains of several different minerals, jump to the rock chart. If it looks like one material, use the mineral charts.
2. Decide: metallic or not? Tilt it under a lamp. If it shines like polished metal, use the metallic chart. Glassy, pearly, silky, waxy or dull means the non-metallic chart.
3. Find the hardness. Try a fingernail (about 2 to 2.5), a copper coin (about 3), a steel nail (about 5 to 5.5), then see whether the rock scratches glass (about 5.5). Rub each mark to be sure it is a real scratch and not a smear of metal.
4. Check the streak. Rub it hard across the unglazed tile and note the powder color.
5. Confirm with the tell-tale clue. For the two or three rows still standing, run the test in the last column: a magnet, a drop of vinegar, a look at how it breaks.

Mineral chart, part 1: metallic minerals

These shine like metal. They tend to feel heavy, and their streak is almost always dark, which makes the streak column especially useful here.

Mineral chart, part 2: non-metallic minerals

These look glassy, pearly, silky, waxy or dull. They are ordered from softest to hardest, so the hardness column reads top to bottom.

Why "white or none" for quartz and garnet? A streak plate is unglazed porcelain, and minerals harder than about 6.5 are harder than the plate, so they scratch it instead of leaving powder. Our streak test guide covers that and other streak surprises.

Rock chart: common rocks

Rocks are mixtures of minerals (or glass), so a single hardness or streak value makes little sense. This chart lists what each rock is made of and the quick test that separates it from its look-alikes.

Marble and quartzite are the classic pair: they can look almost identical, yet the University of Auckland notes that marble can be scratched by a metal blade and fizzes in dilute acid, while quartzite does neither. If you want the bigger picture of how these rocks form, our hub on types of rocks explains igneous, sedimentary and metamorphic rocks, and rock vs mineral explains why the rock chart looks different.

How do you read the chart top to bottom?

Treat each column as a gate, and only look at the next column for the rows that made it through.

Example 1: a brassy, metallic nugget. The metallic chart has three brassy rows: pyrite, chalcopyrite and gold. A steel nail cannot scratch it, which rules out chalcopyrite (3.5 to 4) and gold (2.5 to 3). The streak is greenish black, which fits pyrite and not gold. Result: pyrite, also known as fool's gold. Real gold is soft, dents under a pin and is far heavier (a density of 19.3, against about 5 for pyrite).

Example 2: a heavy, black, metallic lump. Hematite and magnetite both fit the first three columns. The streak splits them instantly: reddish brown means hematite, black means magnetite. The fridge magnet confirms it, because magnetite grabs a magnet and pure hematite does not.

Example 3: a white, sugary rock. Grains you can see send you to the rock chart. Marble and quartzite both fit. One drop of vinegar and one scratch against glass decide it.

Notice that color did almost no work in any of these examples. Our how to identify rocks guide explains the full order of tests and why color comes last, and the Mohs hardness test guide covers scratch testing in detail.

When does a rock identification chart fail?

A chart is only as good as the surface you test and the list it covers. These are the usual trouble spots.

• Weathered surfaces. Rust stains, dark desert varnish, lichen and chalky rinds hide the real color and luster. Test a fresh, broken face instead, and wear safety glasses when you break it.
• Mixtures. A scratch test on granite gives a different answer depending on which grain you hit. Test single grains with a hand lens.
• Grains too small to see. Basalt, chert and shale are made of grains you cannot test one by one, so lean on texture, weight and the quick tests.
• Colors that vary. The same mineral comes in many colors. Quartz alone appears clear, white, purple, pink, yellow and smoky.
• Things that are not on the chart. Slag (glassy, bubbly furnace waste), concrete, brick and bottle glass all turn up in gardens and gravel. A possible meteorite belongs in the free meteorite checker, not a rock chart.
• Rarer minerals. Far more minerals exist than any chart can hold. This one covers the ones beginners find most.

The RockhoundID app, coming soon, will suggest likely matches from a photo and tell you which test on this chart confirms them.

The takeaway

A good rock identification chart is really a checklist. Decide metallic or not, find the hardness, check the streak, then use the tell-tale clue to settle the last two or three candidates. When nothing matches, look for a fresh surface, think about mixtures and man-made look-alikes, and remember that a chart gives you likely candidates, not a final verdict.

RockhoundID guides help you narrow down what you found. They suggest likely candidates, not certain identifications or appraisals. For anything valuable, rare or possibly from space, ask a museum, a university geology department or your state geological survey, and check the collecting rules for the land before you take anything home.