Collini, Cosimo (1727-1806). Journal dun voyage qui contient differentes observatons mineralogiques; particulierement sur les agates, et le basalte. Mannheim, 1776.
Cosimo Collini was the director of the natural history collections of the Elector Carl Theodore of the Palatinate, in Mannheim. Mannheim lies along the Rhine, upriver from Mainz, and Collini visited the area north of Mainz and gave one of the first descriptions of basalt formations along the Rhine. He provided a picture of the basalt river rocks around Unckel (now Unkel), which boatmen called "Unckelstein"; the basalt is visibly blocking traffic in the river.
Directly across the Rhine from Unkel is a basalt quarry called Oberwinter, which was mined for its basalt building material. The same plate shows the Oberwinter site, opened up, with many basalt columns in full view.
For a detail of the river view at the bottom of this plate, see the introduction to this section (Basalt along the Rhine).