Bavin

[…]that hot love is soon cold: that the bavin, though it burn bright, is but a blaze: that scalding water, it if stand awhile, turneth almost to ice[…]

The concretions […] are called 'bavin,' the shale associated with them being termed 'rotch.'

The skipping King, he ambled up and down, / With shallow jesters, and rash bavin wits, / Soon kindled and soon burnt, carded his state, / Mingled his royalty with capering fools,