Bare Earth Elements: Bone up on your spooky geo-vocabulary this Halloween

by Timothy Oleson
Tuesday, October 31, 2017

This list of Halloween geo-jargon is full of fire and brimstone. Or at least brimstone, which of course is just sulfur. Smelly, but not all that scary on its own. Credit: Nadj91, CC0

I simply couldn’t resist writing this post. While I’m hardly a fanatical Halloween guy, I am an impassioned lover of puns and word humor (typically, the more Dad-like, the better in my book). And so when it occurred to me I could crack open my big ol' “Glossary of Geology” to scour it for some of the eerier sounding jargon within, it seemed a perfect way to acknowledge the day. Fear not … unlike with H.P. Lovecraft’s “Necronomicon,” there are no ancient or evil powers to be conjured from the netherworld by speaking these ghastly glossary entries. You might, however, summon an appreciation for the some of the fiendish creativity and ghoulish humor that’s gone into earth science’s vast lexicon.

You’ll note that I haven’t listed any spooky-sounding place names or specific geologic features — the list of locales with “Devil” in the name could fill a book on its own. I was going to go with 13 terms as that seemed like an appropriate number, but a last-minute search led me to one more item I had to add, so a random 14 it is. Of course, there are many others, so feel free to contact us in the Twitter-verse (@earthmagazine) or on Facebook to share any that you’d add. Enjoy!

No list of spooky geo-terms would be complete without bloodstone. Credit: Ra'ike, CC BY-SA 3.0


Glossary of Geology (GoG) definition: A semitranslucent leek-green or dark-green variety of chalcedony speckled with red or brownish-red spots of jasper resembling drops of blood.

An obvious choice, but one that’s hard to skip on a Halloween-themed list. Also known as heliotrope, bloodstone is primarily chalcedony with bits of reddish jasper, according to the Glossary; although other sources note that the “drops of blood” can also come from hematite.

Ghost coal

GoG: A coal that burns with a bright white flame.

This coal is known to contribute to anthropogenic apparitions — er, make that emissions.

Tastes like... blue raspberry? Credit: Rob Lavinsky, CC BY-SA 3.0


GoG: A blue spinel.

A slight stretch maybe, but I had to squeeze in some reference to candy — it’s Halloween after all! Besides, this variety of spinel — which is also known as ceylonite — is named for a part of Sri Lanka called Kandy, which Mindat spells as Candy … so I think it totally plays.

Phantom crystal

GoG: A crystal within which an earlier stage of crystallization or growth is outlined by dust, tiny inclusions, mineral coatings, or bubbles, e.g., serpentine containing a ghost or phantom of original olivine.

Also known as a “ghost crystal.” Internet searches mostly turn up examples of phantom quartz — some of which are imbued with mystical or healing powers (and can be purchased for a low low price!) — but there are other examples to be sure, including the Halloween-appropriate mention of serpentine in the GoG entry.

A pale green specimen of hellyerite from Tasmania. Credit: Leon Hupperichs, CC BY-SA 3.0


GoG: A pale blue monoclinic mineral: NiCO3·6H2O

With a name like hellyerite, you might expect this nickel carbonate mineral to have a reddish or orange coloration instead of pale blue or green. Then again, it wasn’t named for the underworld, but rather for Henry Hellyer, an English surveyor known for his exploration of Tasmania.

Dead cave

GoG: A cave in which there is no longer any moisture or any growth of speleothems associated with the presence of moisture.

A scary place no doubt, where you might find the preserved remains of the formerly living (also known as fossils). Also perhaps a nightmare for an isotope geochemist searching for records of recent climate. “The speleothems [gasp] … they’re dead! They’re all dead!”

A most frightful spider diagram.

Spider diagram

GoG: A graph in which the vertical axis is the ratio of the concentration of a trace element in a sample to the concentration of that element in some reference material (average chondritic meteorite, estimated primitive mantle, etc.). On the horizontal axis the elements are arranged in order of their bulk partition coefficients.

Also called “spidergrams,” these things can definitely be scary up close, and they’ve certainly haunted the dreams of many a geoscience student. The description alone is enough to make me cringe.

Zombie effect

GoG: Apparent range extension of the fossils of an extinct organism due to reworking of those fossils into younger strata by sedimentary processes.

Ok, so it’s not exactly “The Walking Dead” or “World War Z,” but earth science’s version of the zombie effect can sometimes throw a wrench into our understanding of the fossil record.


GoG: One of the series of related and triangular or lune-shaped sections of a map or chart, usually bounded by meridians and tapering to the poles, which can be applied to the surface of a sphere to form a globe.

So, you know how when a globe projection is flattened onto two dimensions, it looks like a side-by-side lineup of pointy, surfboard-looking shapes? Those surfboards are called “gores.” News to me!

Batt, or bat, is black shale like this interbedded with layers of coal. Credit: James St. John, CC BY 2.0


GoG: An English term for a compact black carbonaceous shale, which splits into fine laminae and is often interstratified with thin layers of coal or ironstone.

Also spelled “bat.” I almost flew right by this one under “B” in the glossary. Luckily, my sixth sense (echolocation perhaps?) for frighteningly bad puns kicked in and led me to it.


GoG: An organism with extreme departure in form or structure, generally pathologic, from the usual type of its species.

Is this the most scientific-sounding definition of a monster you’ve ever heard or what? Imagine trying to explain to a young child that there isn’t an “organism with extreme departure in form or structure, generally pathologic, from the usual type of its species” under the bed. Or maybe, there is … BOO!

Good old fashioned brimstone. Credit: Tim Evanson, CC BY-SA 2.0


GoG: A common or commercial name for sulfur, especially native sulfur or fine sulfur fused into rolls, sticks or blocks.

How and when sulfur became known as brimstone I do not know. But I suppose ardent depictions of “fire and brimstone!” do evoke a more visceral sense of terror than scenes of “fire and sulfur!”

Devil’s slide

GoG: (a) An avalanche track down a steep slope. (b) A long narrow mass of talus material descending a steep mountain.

Even if you’re tall enough, I’d recommend skipping this roller coaster.

And last but not least…

An excerpt describing necronite, or "fetid feldspar," from Parker Cleaveland's 1822 work, "An Elementary Treatise on Mineralogy and Geology."


GoG: A blue pearly variety of orthoclase that emits a fetid smell upon hammering. It occurs in limestone near Baltimore, Md.

With a name suggestive of death, and perhaps a smell to match, there was no passing this over on my list of Halloween geo-jargon. The definition in the GoG starts off well… “A blue pearly variety of orthoclase” sounds lovely, right? But this is no ordinary potassium feldspar, but one that unleashes “a fetid smell upon hammering.” If it were living, I’d think this smell was an evolutionary adaptation that conveniently wards off predators. I confess to a morbid — er, let’s say scientifically curious — interest in smelling it myself someday. Thankfully, I live just down the road from Baltimore. (Side note to my wife: If you need me next weekend, I’ll be out sniffing limestones.)

Incidentally, necronite is hardly the only mineral known for putting out a pungent smell. There is of course the aforementioned brimstone, with its charming rotten egg odor. And among others, native arsenic is said to smell faintly of garlic when rubbed or heated (best NOT to try this one at home), selenium minerals can smell of horseradish, and antozonite, a variety of fluorite, is also known as “stinkspar” or “fetid fluorite.”

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