Well it seems that one has to come up with names for everything when you blog so this is my “dark magma heart”:
It is a pseudosphere: a hyperbolic version of a cone. I read A Field Guide to Hyperbolic Space (as as I wrote about here) and of course rushed out to my stash and grabbed some yarn I had left over from a secret project (I wrote about this yarn already here).
So this is the result.
These are fun. It is constructed by crocheting one stitch at the centre then working in the round, increasing into every second stitch. It starts out as if it were nothing special and getting more exciting every round. I left the tail at the centre as the centre of a pseudosphere as the centre point reaches infinity; you could also hang it from something.