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Monday, January 30, 2012

Accretionary Wedge #42: Countertop Geology

This time around it's volcanoclast sending out the call for posts for this round of the Accretionary Wedge, asking geobloggers about countertop geology.  Because pretty much everyone knows that the best countertops in a kitchen or bathroom are made of granite... or are they?

Although natural stone as countertop or tile is sold as either "granite" or "marble", they are often neither of those.  The divisions "granite" and "marble" generally mean two kinds, the first being hard countertops made of silicate minerals and softer ones made of carbonate minerals.  The term 'granite' is applied very loosely!

And that's the case with mine.  A few years ago, my wife and I bought a house and the kitchen needed a total gutting.  So before we moved in, we spent about a month tearing out the old kitchen and building the new one.  While searching for something to use as a countertop, we came across a pile of "granite" tiles that I HAD TO HAVE.  The stone was a black & white gneiss, a metamorphic rock.  They were on a deep discount so we took home enough to cover the area we had planned for the counter.  I then got to cut the tiles with a tile saw to fit, glued them down to the base we had built, and filled it in with grout.  Cutting the stone tiles was good fun, of course!

The gneiss had large white feldspar clasts and tiny little folds in the foliation, and consequently was loaded with shear sense indicators - and yes, I did have them all going the same direction  :-).  I had my students in structural geology over a time or two for "lab" where they had to find & sketch some of them... and then we made home-made ice cream... you know, for the thermodynamics lesson about enthalpy with mixtures of ice & halite, or something...

We sold that house and moved to another a couple years back, and unfortunately we lost a lot of pictures that I had taken of the countertop.  But, fortunately, some of the pictures of the kids had been backed-up, and I managed to find one of B that shows the countertop in the background.  So if you can manage to look past this adorable blue-eyed blondie who doesn't have all her teeth yet, you'll see the gneiss in the background.

And here's a cropped, zoomed in version.