I was looking for rocks the other day at one of the GeoDig sites and after
finding a few, I went to my satchel to identify them. Much to my surprise, while I was
looking at the drop down list of names of the different rocks I found and the ones they could be, I discovered there was an extra rock that was not listed!
Gneiss is the name of the mystery rock. After
talking to some of my friends about this rock that wasn't there, my curiosity
got the better of me and I decided to research it to see if it was even a
real rock.
After searching for ages on the net, I finally came up with
this: Gneiss is a high-grade metamorphic rock, which is basically saying that
it has been subject to more heat and pressure than schist or other
metamorphic rocks. It is also coarser than schist. The rock has bandings that
go around the rock -- these bandings are formed by the different minerals that
make it up, such as quartz, mica, feldspar and hornblende.
Gneiss can be formed by a sedimentary rock such as sandstone or shale or it can be formed
from the metamorphism of granite. Gneiss is mainly used as a paving or
building stone.
If anyone else has found this rock at the GeoDig sites, I would love to know.
Until then, this is javagirl, going to look for her rocks!
