Graywacke

Part of speech: noun

Definitions

1. A sedimentary rock marked by its dark hue and inconsistent grain sizes, which is composed of quartz, feldspar, and various rock fragments while usually forming in low-energy settings
2. This dark-colored sandstone, distinguished by its variable grain structure and texture, contains a blend of quartz, feldspar, and other rock debris, typically originating in environments with limited energy
3. A type of dark-hued sedimentary rock characterized by a mixture of quartz, feldspar, and assorted rock fragments, commonly formed in low-energy environments

Etymology: "Graywacke" is an American spelling of "greywacke," a dark, hard sandstone, and the English word is simply an anglicised form of the German "Grauwacke." That German name, roughly "grey rock" or "grey earth," was the term used by the German miners and geologists who first worked with this stone in the mountains of central Europe, where it was familiar to them long before it had a settled scientific meaning. English took the word over in its German shape and gradually adapted it to English spelling. The "gray" spelling, which the source records as an alternative, is the form that became common in American usage, while "greywacke" keeps the older British look. Both spellings point back to the same German root, so the colour in the name is the one thing the word has always kept.