Admittedly, I love rocks. I actually get a little giddy when I'm on a hike or driving on a road trip and I recognize a particular geologic formation, or even simply coming across a neat rock on the trail. For me there is just something so fascinating about walking around on this earth and taking into account the amazing processes it went through to get where we are today. Of course this entails dramatic acts of geologic magic over millions and millions of years, which honestly I sometimes find a little overwhelming (although I do love to day dream and fast forward the Flatirons of my hometown from non-existence to existence in the matter of a few seconds). This is why rock specimens are so much fun. They are like a mini portal to a very big event.
Take this lovely rock for example. Named for the German chemist and mineralogist Johann N. von Fuchs (1774-1856), it is a relatively common form of Muscovite Mica. The beautiful emerald green coloring comes from trace amounts of chromium found in the structure of the rock's crystals.
This particular specimen has a lot of variation in it, which I love. With in a 9" by 2" space I can see the difference between the small and larger crystals, dull and shiny appearance and rough and smooth textures. In the example above the crystals are very small, giving the rock a shiny almost opaque appearance.
Coming from the mica family Fuchsite has a hardness of 2-2.5, and has no streak color. Originally reported in austria, it can be found in many places around the world. This particular specimen comes from Brazil.
Another interesting quality of Fuchsite is its perfect basal cleavage. No not that kind of cleavage, cleavage in the context of geology. I think of cleavage in the way a rock will break apart. In the case of micas the cleavage is "perfect" because it separates perfectly into thin sheets, as opposed to shattering into many small pieces.
I have been a fan of micas for a long time. As a kid I would collect the tiny flakes of mica I found in the sand or gravel in the play yard at recess ad pretend if was precious metal for my treasure chest. I knew that mica, especially of the Muscovite variety comes in many different colors, but I had only ever seen the basic white/silver and black (biotite) micas. That was of course until my sister stumbled upon this particular variety at a local rock shop, and I am so very glad she did!
I've said it before, and I'll say it again (with pride), geology rocks!
~Jordan
*Last time in Nature: Eye Spy, New Friends
