Azurite (a hydrated copper carbonate) is an intense azure blue found in the oxidized zones of copper deposits, almost always intergrown with green malachite — the pair on one specimen is itself a strong identification. Confirm with the light blue streak, low hardness, and effervescence in dilute acid. Over time azurite weathers to malachite, so green-rimmed blue crystals are common.
Field identification workflow
- Confirm the color: azurite is a deep azure blue with no green tint of its own — any green on the specimen is almost certainly intergrown malachite.
- Run a streak test: light blue on unglazed porcelain. No other common blue mineral leaves it.
- Check hardness (3.5–4): a knife scratches it easily; it will not scratch glass.
- Apply one drop of cold dilute acid to an inconspicuous corner: brisk effervescence confirms a carbonate.
- Look for the company it keeps — green malachite rims and crusts on blue crystals record azurite weathering in place.