From a photo caption in the section "Around Kilauea" in Hawaii the Big Island Revealed: The Ultimate Guidebook, 5th Edition, by Andrew Doughty:
'A'a lava on the left (named by the first Hawaiian to walk on it barefooted) is rough and clinkery.
The 'a'a lava in the photo looks like a cascade of giant Grape Nuts, overly roasted and somewhat charred, and of various sizes. Up close the formation is highly porous and sure to cut your feet. Clinkery makes the lava sound downright friendly. One might think, "Rolling chunks of this lava make a pleasant clinking sound."
The OED includes clinkery as one of its Obs. rare words; it means "Contracted or shrivelled with heat or cold." One 1398 spelling has the word as klynkery.