slatestone

I dipped the pen into the inkhorn, and put the paper which he had torn from the prayer-book on a flat, smooth piece of slatestone.

The Birthright Joseph Hocking 1898

With a hammer and chisel I can cleave them into flags; indeed these flags are employed for roofing purposes in the districts from which the specimens have come, and receive the name of 'slatestone.'

Fragments of science, V. 1-2 John Tyndall 1856

It is composed chiefly of sandstone intermixed with an iron ore of bad quality; near the bottom is a soft slatestone with pebbles.

History of the Expedition Under the Command of Captains Lewis and Clark, to the Sources of the Missouri, Thence Across the Rocky Mountains and Down the River Columbia to the Pacific Ocean 1814

The banks along the low grounds are of a rich loam, followed occasionally by low bluffs of yellow and red clay, with a hard red slatestone intermixed.

History of the Expedition under the Command of Captains Lewis and Clark, Vol. I. To the Sources of the Missouri, Thence Across the Rocky Mountains and Down the River Columbia to the Pacific Ocean. Performed During the Years 1804-5-6. William Clark 1804

It is composed chiefly of sandstone intermixed with an iron ore of bad quality; near the bottom is a soft slatestone with pebbles.

History of the Expedition under the Command of Captains Lewis and Clark, Vol. I. To the Sources of the Missouri, Thence Across the Rocky Mountains and Down the River Columbia to the Pacific Ocean. Performed During the Years 1804-5-6. William Clark 1804