Day #112 Deskcrop: Nepheline Syenite, Stettin Complex

I feel much more confident of the locality of today’s deskcrop. This is due in no small part to the fact that an ILSG field guide to this particular locality is online in PDF format. The sample is a piece of nepheline syenite from the southern edge of the ~1520 Ma Stettin Syenite complex, located not far to the northwest of the Wausau Syenite featured back in March. This sample is one of my favorites for teaching about differential weathering of minerals – the large crystals of nepheline (a variety of feldspathoid), abundant in this sample, weather much more rapidly than the feldspars, giving the weathered surface of the sample a distinctive pitted texture (best seen in the second photo below).

IMG_1257
Nepheline Syenite, Stettin Complex

IMG_1259
Nepheline Syenite – note the pitted nepheline crystals

Explore this and all of my 2010 Deskcrops and Outcrops in Google Earth!

Bookmark the permalink.

Comments are closed.