Even if you've only taken one science course in your whole life, chances are good you got a dose of jargon: scientists are big on naming things, pigeonholing them into ever-smaller pigeonholes in hope of understanding them better. A side effect of the urge to classify is that scientists have to keep inventing new words and combining old words in new ways.

Well, geologists are as bad about jargon as any other discipline and, like all the others, the earth scientists have come up with plenty of strange words and incomprehensible definitions; and a few inside jokes. So without further ado, here's a brief list of some weird geology words - accompanied by definitions, real and imagined.


PhonoliteCredit: Ohio State UniversityNope, it's not a fake rock, though that would be a good definition. Lots of rock and mineral names end with "-ite," and this fine-grained extrusive igneous rock is no exception. To the naked eye, it looks like a hunk of garden-variety basalt (a black rock that forms from lava flows), but under a microscope it turns out to have some pretty weird mineralogy. It's almost entirely alkalai feldspars, if that means anything to you.

The funny part, however, isn't that it's an extrusive igneous rock that's mostly feldspars; the funny part is that it's called "phonolite" because when you hit it with a hammer, it rings. No kidding...

Welded Tuff

Welded TuffThis name always sounds to me like it belongs in an advertisement for trucks -- "The 2015 Dodge Ram: It's welded tuff!" -- but it's really a rock made of volcanic ash. That's the "tuff" part; it's called "welded" because the ash was falling so fast that the heat in the middle was enough to bake it hard. It's been "indurated by its own heat," sort of like a giant geological MRE.


GraywackeCredit: Valdosta State UniversityThe "gray" is easy, and the "wacke" part of this rock name is pronounced like it looks. That might be why some people think geologists are a pretty "wacky" bunch. Or not.

Most sandstones are some shade of brown or tan because they're made up of little grains of quartz sand. Graywacke is sandstone, too, though tiny grains of rock are most common. Surprisingly enough, it's often a shade of gray.


A crystal of molybdeniteCredit: Michigan Tech University

Try saying "molybdenite" fast five times. Heck, try saying it once! It's a mineral that's the principal ore of the metal molybdenum (which is hard enough to say), a silvery-gray mineral that's so soft that you can write with it on a piece of paper like a pencil. Miners call it "Molly" -- go figure.




YardangsCredit: University of Arizona / NASA / JPL

Sounds like a curse, or perhaps some kind of martial arts weapon, doesn't it? You know, like maybe a Japanese shuriken or a Klingon batliff? It's actually a sharp-edged ridge with a round-bottom troughs on both sides, formed by wind erosion in arid regions. Not a bad Scrabble word, though.




LeaveriteCredit: pippalou / morguefile.com

A sort of a field-tripping geologist joke: if you don't know what a rock sample is, it's a "leaverite": leave 'er right where it is.

It's the only type of rock found in national parks, by the way.





HornfelsCredit: Ohio State University


Sounds sort of like a fraternity or a men's dorm... Sorry, though, it's just a fine-grained rock formed by contact metamorphism. Really rather boring.




Myrmekitic texture in thin sectionCredit: Union College

Fun-looking word, no? "Myrmekite, my myrmekite..."

Myrmekite is the intergrowth of alkalai feldspar (plagioclase) and vermicular quartz, formed in a non-igneous environment. Vermicular, by the way, means "worm-shaped"; though these "worms" are microscopic in size.



Potential lizarditeCredit: Ken Lund / flickr.com


Not really a rock, more of a state of mind: any flat rock where a tired geologist can bask in the sun after lunch - like a lizard. Also a mineral in the serpentine family, which makes it related to asbestos.



CactusCredit: Xandert / morguefile.comMost geologists who run across this definition in the Glossary of Geology[1] think it's probably a joke (and it probably is):

"An irregular, intrusive igneous body of obscurely cactus-like form, more or less confined to a horizontal zone and appearing to consist of irregularly related and possibly distorted branching and anastomosing dikes that fed a laccolith... 'a quasi-horizontal chonolith composed of anastomosing ductoliths whose distal ends curl like a harpolith, thin like a sphenolith, or bulge discordantly like an akmolith or ethmolith.'"


Diagram of a palinspastic restorationCredit: University of Tubingen (Germany)


Nope, it has nothing to do with 2008 preseidential electoral politics: it's a word that relates to paleogeographic or paleotectonic restoration; which is a sort of roundabout way of saying, "Putting everything back the way it was before it got moved."



In closing, my favorite geology bumper sticker:

I'm a geologist; I'll make your bedrock.