A thin coating of green malachite on matrix. Glossy, as if it had been coated with something (but it's not...). Different from all the Mexican malachite photos posted on Mindat, making me believe (at first) this might be pseudomalachite. However it bubbles vigorously with muriatic acid to produce a yellow green solution (just like malachite). Came to me as part of a flat labeled "Malachite, Mexico", so I will retain that species and locality information. If you have an alternate idea I'd certainly like to hear it! Minor azurite veins also present.