Dominican Amber (La Toca Fm., 20.43-13.65 Ma)

4.7g piece of amber from the La Cumbre Mine, measuring (mm) 25x22x15. It has a couple marcasite inclusions: seen here is a protruding portion (one half remains inside the piece) that was perhaps a gas bubble, but later infiltrated with iron and sulfur in solution during burial, migrating via a fracture/microfracture; or it may be a permineralized organic/inorganic inclusion (shell, quartz pebble, etc.), which are documented in amber from the La Cumbre deposit, and is called "double fossilization": while this occurs in tiny grains of younger La Cumbre amber which were deposited after the older amber seen here, it is possible it is seen in this older La Cumbre material. Another example of double fossilization is known from fully pyritized insects with marcasite interiors, recorded from cretaceous amber in NW France.  There are dozens of visible dual-phase, countless single-phase, and at least two triple-phase bubbles. "Pyrite disease" is a major concern with this specimen; even with preservation in an airtight container, oxidation is still possible, given the presence of gas/liquid inclusions, and the fact that water and gases do penetrate and migrate within amber over time. Portions of the piece may be doomed, but it is interesting while it lasts.