This 'double replacement pseudomorph' specimen began as a small cluster of azurite crystals nestled in a limonite matrix cleft. Over time the azurite was replaced by chemically-similar malachite with retention of the original azurite morphology. In a second wave of replacement, malachite was altered to chrysocolla, producing the final product seen here. (Also possible for the original species to have been malachite, making this a single replacement.) A tiny bit too large to fit into a standard 'Perkie' thumbnail box when mounted on an appropriate acrylic base, but might be trimmable.