Embedded part of basalt pebble, east wall 'stores hut'.
Grits comprising 3 mm-sized rounded clasts and conglomerates with pebbles up to 5 cm in size are also present.
We will then have compressed the pebbles to all lie on 1 and its neighbouring vertices.
Typically, most of the pebbles are coated by iron hydroxide.
It penetrates coarse sand more readily than fine, and fine sand than wood ash, and burrows easily in fine sand with pebbles.
There then follows another change in sediments with some breaks (including coarse sandstones with pebbles), which indicate strong activation of volcanicity.
The facies is generally reverse-graded with an imbricated pebble layer at its top.
This would, of course, readily account for the good fit between the pebble shape and the underlying sandstone.
