slgwv's photos with the keyword: erratic

With glacial erratic. Looking southwesterly; the Blue Lakes Highway crosses the valley just on the other side of the meadow. Sierra Nevada, California. Yes, there is a "Hope" and "Faith" valley in the vicinity, too! ;) The inset shows an erratic-less view. Taken off the Charity Valley trail. The peak across the valley is unnamed, according to the USGS 7.5' topo map.

Granite boulder that's been lying there since the Pleistocene glaciers melted. Just off the Pacific Crest/Tahoe Rim trail, Sierra Nevada, California.

Well, no. ;) It's not even a conglomerate, altho it looks like one! It's mostly granite, with the large round things weathering out being pods of more iron-rich rock. "Mafic inclusions", in the jargon. Their composition is basaltic, and it's now thought these could reflect "liquid immiscibility"--like oil and water, the granite magma and the basaltic magma didn't mix, with the basaltic liquid forming large "drops." The boulder itself is a glacial erratic. Sierra Nevada, California, USA, near the Blue Lakes.

Been lying there since the glaciers retreated at the end of the Pleistocene, ca. 10K years ago, and is slowly breaking up in place. It's a piece of granite with iron-rich (mafic) inclusions, which are the dark spots weathering out. There are lots of erratics lying around all over this area.