Glendonite is an anhydrous, but structurally identical, version of ikaite, a mineral which forms only in near-freezing alkaline water. During a talk about how he was able to infer what the Arctic climate was like in Cretaceous times, the speaker described the technique he had used to search for this unusual material below the icy waters of Alaska. I felt that a Health and Safety warning was needed.

When next in the Arctic, ignore all advice sheets!
Geologists there who are looking for clues
About palaeoclimates, especially ice-sheets,
Should strip to their T-shirt, take off their shoes,

Then jump in the water (it’ll be nearly freezing)
And wiggle their toes in a meaningful way.
(There’s a breed of geologist to whom this is pleasing,
Though quite why that’s so, I really can’t say.)

The object of this masochistic endeavour
Is to feel for a glendonite lump with your toe;
And then you can say, feeling ever so clever,
“It was glacial once in these parts, don’t y’know!

“For glendonite used to be ikaite, see?
A hydrated calcite, that forms
In alkaline water as cold as can be,
But it changes as soon as it warms.”

(It loses its water, but its shape stays impressed –
It’s a pseudomorph, so I am told.)
But don’t spend too long on your glendonite quest
Lest you perish because of the cold. . .

[Image: NASA, Goddard Institute for Space Studies]
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