Extrusive calciocarbonatite (calciocarbonatitic lapillistone; welded calciocarbonatite) (7.4 cm across), erupted during the Miocene from Germany's extinct Kaiserstuhl Volcano.

The German rock shown here is famous among carbonatite researchers. It comes from the first ancient carbonatite ever demonstrated to have originally been surficial volcanic material (extrusive origin). As are most carbonatites, this rock is composed of calcite (calcium carbonate - CaCO3), and it bubbles in acid. The tannish-brownish-grayish portions of the rock consist of rounded to subrounded particles - those are carbonatite lapilli from an ancient volcanic eruption. The white portions of the rock represent calcite cement that binds the lapilli together.

This extrusive calciocarbonatite is from the ancient Kaiserstuhl Volcano, formed along a continental rift called the Upper Rhine Graben. The long-extinct volcano is now eroded away, but some of its extrusive rocks and much of the originally-underlying intrusive complex is still preserved.

Age: Langhian to Burdigalian, late Early Miocene to early Middle Miocene, 14-18 million years.