This is the last of my set of posts on Oakland building stones, although I reserve the right to come up with more. What you’re looking at below is gneiss on the wall of the Lionel Wilson Building, in City Hall Plaza.
Gneiss is a fun rock, for me anyway, because when I see it I think, “Nice.” And that’s exactly how the word is pronounced.
Gneiss is made of the same kinds of minerals that granite is — quartz, feldspar, garnet, hornblende — and stone dealers call it granite. A large share of your granite countertops are actually gneiss.
The difference is that strongly directional fabric, in which the mineral grains are stretched and aligned and separated into bands and stripes. Gneiss, you see, is actually a metamorphic rock, squeezed like taffy under high heat and temperature.
That fabric, and nothing else, is what defines gneiss. The fabric is called gneissosity (and geologists will skunk you in Scrabble because they know words like this).
Here’s a gneiss boulder I used to keep as a pet. I gave it a new home by slipping it into the front yard of a home with lots of other cool rocks.
And here are two gneisses I photographed in New York. The first one is a garnet gneiss, a quarry-faced ashlar in the wall of a cemetery visitors center.
And the other one is a wild boulder near Albany, the New York Albany.
Gneiss is a stone of infinite variety. The pink-and-gray stone in the Wilson Building is probably Morton Gneiss, an extremely old stone quarried in Minnesota. David B. Williams, author of the very fine Stories in Stone, considers it America’s most beautiful building stone. I’ve posted other examples from Oakland here and here.