A useful identification photo shows the whole rock clearly, with enough detail to see its surface and a ruler to show its size. You can do this with a phone, a plain background and daylight from a window.
Before you send a photo to an app, museum or mineral club, check three things: is the rock sharp, is the color believable, and can the reader tell how large it is? The Oxford University Museum of Natural History asks for well-focused, well-lit photographs with a ruler for scale.
In this article: light and background · useful views · notes to keep · before you send.
Set up the light and background
Place the rock on plain gray or tan card near a window. Indirect daylight is a good starting point; direct sun can produce harsh glare. Check that the background is free of patterns and that the whole specimen fits in the frame. These are the California Geological Survey’s recommendations for identification requests.
Wipe the camera lens, then tap the specimen on the screen to focus. Enlarge the photo afterward: if the edges and grains look soft, move back a little and try again. Hold the phone steady while it takes the picture.
Leave color filters off. If a bright patch hides part of the surface, change the camera angle or move the setup to softer light. You want a reader to see the texture in that patch.
Take a few useful views
Start with one picture of the whole specimen and a ruler beside it. Keep the ruler close to the same level as the rock so the scale is easy to read. Follow with another side and a close view of an interesting feature, such as visible grains, bands or an existing broken surface.
The Sedgwick Museum of Earth Sciences asks for photographs from different angles with a ruler. A close-up adds detail, while the wider view shows where that detail belongs.
Keep the same background as you turn the rock. This makes the set easier to compare. There’s no need to break, scratch or chemically clean a specimen for a photograph.
Keep the story with the photo
Record where the specimen came from, including whether you found it in place, picked it up loose or bought it. The California Geological Survey emphasizes location information when identifying a specimen.
A simple note can hold the details you might otherwise forget:
- Specimen label: a short name or number that also appears in your photo filenames.
- Where it came from: place found, or the seller’s description if purchased.
- Size: length, width and height with units.
- Condition: dry, wet, polished, coated or altered, if known.
- What caught your eye: bands, visible crystals, holes or another feature you want explained.
Keep a seller’s label with the record even if you’re unsure it is correct. It gives you something specific to check later.
Check your photos before you send them
Open the files at full size. Keep the clearest whole-specimen image and the views that show something different. Check that the ruler is readable and your fingers aren’t covering the feature you’re asking about. If you have several specimens, give each its own label and photo set.
Good photos help someone choose possible matches, but they cannot measure physical properties such as Mohs hardness. A photo search can still be a good first step: our article on using Google Lens to identify rocks shows how to treat its suggestions as leads. For a clear piece, the quartz vs calcite guide explains what to check next, and quartz vs glass covers glass-like finds.