Crossword-Solution: PITCHSTONE 10 letters, 6 clues 🏆 scrabble score: 17

And the expedition ended in an untravelled corner of the Yellowstone Park, near Pitchstone Canyon, where he and young Lin McLean and others were witnesses of a sad and terrible drama that has been elsewhere chronicled.

The fragments of scoriae, embedded in the crystalline calcareous basis, are of a jet black colour, with a glossy fracture like pitchstone.

Secondly, small irregular nodules of the obsidian, either standing separately, or united into thin layers, seldom more than the tenth of an inch in thickness, alternate repeatedly with very thin layers of a feldspathic rock, which is striped with the finest parallel zones of colour, like an agate, and which sometimes passes into the nature of pitchstone; the interstices between the nodules of obsidian are generally filled by soft white matter, resembling pumiceous ashes.

Most of these dikes are coated by a glossy layer, from one to two-tenths of an inch in thickness, which, unlike true pitchstone, fuses into a black enamel; this layer is evidently analogous to the glossy superficial coating of many lava streams.

Jago, in the Cape de Verde Islands, that where a great stream of molten lava has flowed over a calcareous bottom into the sea, the outermost film, which in other parts resembles pitchstone, is changed, apparently by its contact with the carbonate of lime, into a resin-like substance, precisely like the best characterised specimens of the tuff from this archipelago.