from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun Any of various dark gray sandstones that contain shale.
from The Century Dictionary.
- noun In geology, a compact aggregate of rounded or subangular grains of various silicious rocks, held together by a paste which is usually silicious.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Geol.) A conglomerate or grit rock, consisting of rounded pebbles and sand firmly united together.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun Alternative form of
from The American Heritage® Dictionary of the English Language, 4th Edition
Parts of the Danville Basin, on the other hand, are higher and have more relief than adjacent portions of the Piedmont because they are underlain by relatively resistant rocks including conglomerate and graywacke (Hack, 1982; Virginia Division of Mineral Resources, 1993).
Ecoregion 66c is underlain by Precambrian metamorphic rock, including quartzite, graywacke, and conglomerate of the Lynchburg Formation.
It wasn't made of plastic, but exquisitely carved out of graywacke, the same stone as used for the Narmer Palette, which is similar to slate but has a finer grain.
A fragment of an exquisitely carved graywacke vase proved there had been a royal presence -- such stone vessels were products of royal workshops in the early First Dynasty.
It led up stairs of graywacke, along the brink of slaty cliffs that dropped sheer, hundreds of feet to the stream below.
Is it primitive, or is it graywacke like Catskill Mountains?
I received a specimen of slaty graywacke from Lake Superior.
[Footnote 29: I found graywacke in situ at Iron River, in Lake Superior, in 1826, and subsequently at Presque Isle River, where it is slaty, and fine even grained, and apparently suitable for some economical uses.]
Those streams which originate in, or run through districts of granite, limestone, graywacke, &c., present pebbles of these respective rocks abundantly along their banks, at points below the termination of the fixed strata.
Cruachan more to the quick, had he known all about geology, gneiss, and graywacke, and the Silurian system?