Jay Kaufman of the University of Maryland - College Park loaned us this sample to image.

It is a piece of the Ghaub Formation of Namibia, carbonate diamictite with iceberg-rafted debris attributed to the Neoproterozoic "Snowball Earth" glaciation. A prominent dropstone is located in the middle of this face.

Sample measures 10 cm "tall" (stratigraphic thickness) by 12 cm wide.

Image made as part of the MAGIC project (Mid-Atlantic Geo-Imagery Collection) using Northern Virginia Community College's gigamacro rig, as seen here:

gigamacro.com/gigapixel-macro-imaging-system /