Does geology have anything analogous to the KPCOFGS (Kingdom, Phylum, ... ) hierarchy for rocks and minerals?
Sort of...there are three types and within each type there is a "hierarchy". Of course, it is much different than KPCOFGS and is more lateral...not so much in any specific order.
Volcanic rocks, called igneous, are divided by intrusive and extrusive. Which means did it ever reach the surface. The difference is usually obvious to the eye or touch. Granite is intrusive, so it never reached the surface where the pressure is released, and course grained. Basalt, which was once flowing lava, is extrusive with fine grains. The rate of cooling also plays a role. The faster a rock cools the finer the grains become. Granite cooled very slowly compared to basalt.
Sedimentary rocks are composed of tiny particles that build up over time and are cemented together. Think of sandstone and tiny sand grains. Or limestone and tiny little skeletons of sea creatures mashed together.
The third type, metamorphic rocks, throws a wrench in everything because it can be from any of the types above. Metamorphic rocks are rocks that are changed usually by volcanism or plate tectonics. The intense heat and/or pressure alters them into a new form. Sometimes the form is very similar to the original rock but other times it has changed chemically so much that the previous rock type is a rough guess or unknown.
And then there are the minerals in the rocks...which is endless. Knowing minerals well is key to a geologist. Certain rocks only have certain minerals in them.
I'm downshifting a little here so take the following with a grain of sodium chloride.
What I like about geology and chemistry, is that, in the end, everything comes back around to them. Fossils inspired, and support, the theory of evolution. We owe everything to this hunk of rock we call earth. Two basic gases power the sun and all life as we know it and volcanic activity most likely set the the stuff of life into motion. Everything we feel on our skin is an interaction between sodium and potassium. What IS a thought? Our brains chemically bla bla bla. You get my point.
City people back East where I am from would laugh at my decision to major in Geology and see it as a useless degree, but, I wonder how many minerals and mines were needed to make an iphone. When people say "Save the Earth" they really should say "Save the People" because the Earth WILL be fine. It's the living things that need to worry. The damage we are doing is minor and it's possible that global warming could actually accelerate us to the next ice age. Either way, eventually all the crap we put in the air will end up back in the ground, the planets surface is constantly being recycled as well through plate tectonics, and, the sun will explode and none of this shit will matter. I read the other day that the Andromeda Galaxy is going to collide with the Milky Way before that happens. WTF! These things we cannot truly grasp in our little heads. Castles made of sand fall in the sea, eventually.
I was a Geo major but ended up switching because of the ridiculous amount of other classes required. Calculus and chemistry to the max plus physics and bio. I just wanted to learn about mountains and rocks but to really understand this stuff you have to be a chemist and math major too. I also don't really see joy in working the oil biz. Now it's just a hobby to me and it keeps me my mind grounded. Now I am studying to be a helo pilot, my dream as a kid, and the gi bill is making it happen. A weird switch but I think I just want to work outdoors.
My apologies for this becoming a rant, it's cloudy today and just my .02 cents, and I hope I wasn't offensive. Most will disagree with me I presume. Enjoy what little time we have and do what makes you happy!