Rock identifier app for Android

What you see for each find

For minerals, LithoCanvas shows an estimated confidence and typical properties: hardness, crystal system, color and luster. The result is a suggestion. You can check it with the Mohs hardness test built into the app. The Mohs hardness scale page explains the same test on paper, with everyday tools.

How to identify a rock you found, step by step

Take the photos before you scratch anything, because a scratch cannot be undone.

1. Note where and when you found it. Some rocks are common in one region and rare in another, so the place narrows the list.
2. Photograph the rock dry, in daylight, once whole and once up close. Put a coin next to it for scale.
3. Read the suggestion and the properties the app lists.
4. Check hardness with a scratch test. The steps are on the Mohs hardness scale page.
5. Save the find with notes to your collection.

What a photo can show, and what it cannot

A photo shows color, banding, grain, shape and, in good light, luster. That is enough to rule out many options.

It does not show hardness, streak, density, cleavage or how the rock reacts to acid. The U.S. Geological Survey says that rocks and minerals are extremely difficult to identify from photographs and must be examined in person from all sides. A rock identifier app can give you a starting point to check against those properties.

Mineralogists identify minerals by cleavage, color, hardness, luster, streak and density, as the U.S. National Park Service lists them. A photo covers color and luster at best, so the other four need a hand test. Hardness and streak are the easiest to try at home.

Why two rock identifier apps can give different answers

Look-alikes are the main reason. Quartz, calcite and chalcedony often cannot be told apart from an image alone. Light and angle change how color and luster look, and a single photo shows one side of the rock. Two apps can read the same picture differently, and one app can read two photos of the same rock differently.

That is why LithoCanvas gives an estimated confidence and the properties to check. It does not judge authenticity, safety or value. For valuable pieces, ask an appraiser.

Check the result yourself: three quick tests

Each test gives one clue. Together with the suggestion from the photo they narrow the list, and none of them names the rock alone.

1. Scratch test: try a fingernail, then copper, then a knife or glass on an inconspicuous spot, and write down what scratches. The tool values are on the Mohs hardness test page.
2. Streak test: drag the rock across an unglazed porcelain plate and look at the color of the powder, not the color of the rock. Streak plates are about 5 to 7 in hardness. A rock harder than the plate leaves no colored streak.
3. Vinegar test: put one drop of household vinegar on a small spot and look through a hand lens. Fine bubbles point to a carbonate such as calcite or dolomite. Vinegar reacts more weakly than hydrochloric acid, so the lens matters.

Safety Do not scratch jewelry, collector pieces or paintings. Do not scratch fibrous or dusty materials, and do not breathe dust. Keep vinegar off polished or collector pieces.

Rocks, minerals, crystals and gemstones: what is the difference

A mineral is a naturally occurring inorganic substance with an orderly internal structure and a characteristic chemical composition. Quartz and calcite are minerals. The U.S. Geological Survey defines a rock as an aggregate of one or more minerals. Granite, basalt, limestone and sandstone are rocks.

A crystal is a mineral whose atoms follow a repeating geometric pattern, which is why many minerals grow flat faces and straight edges.

A gemstone is a piece of mineral crystal that is cut or polished for jewelry. A few rocks, such as lapis lazuli, are used as gems too, and some gems are not minerals at all: amber, jet and pearl come from living things.

Rocks fall into three families. Igneous rocks such as granite form when molten rock cools. Sedimentary rocks such as sandstone form from deposits and often show layers. Metamorphic rocks such as marble are older rocks changed by heat and pressure.

For a find, the app suggests a rock, mineral or gemstone and lists properties such as hardness, crystal system, color and luster.

How to take a photo that works

Pebbles and beach finds are rounded by water, so photograph a chipped spot too if there is one. Rough crystals show faces and edges that stand out in light that skims the surface. Never scratch a cut gemstone or a piece of jewelry.

1. Photograph the rock dry, because water changes color and luster.
2. Use even daylight and skip the flash, which puts glare on the surface.
3. Fill the frame with the rock, once whole and once up close.
4. Show a fresh broken surface if there is one. Grain and color are easiest to see there.
5. Put a coin next to it so the size is visible.

Your collection

Save each find with photos, notes and a voice note about where it came from. You can also add entries by hand, search and filter, compare two specimens side by side, keep a wishlist and estimate size with a coin for scale. A glossary explains terms such as crystal system or vitreous luster. Paintings go into the same collection.

Price and privacy

LithoCanvas is free to download and shows no ads. Every account includes 5 free identifications. For more identifications and private cloud sync there are three plans, Explorer, Collector and Curator, billed monthly or yearly through Google Play; you see the price and what is included before you buy. There is no trial that later charges you automatically. Your account, entries and photos are stored in the EU. Photo identification needs an internet connection, and the selected image is sent to the recognition provider only after you agree. You can export your data or delete your account in Settings.