rock-meal

Finely scaly varieties with a pearly lustre are known as argentine and aphrite (German _Schaumspath_); soft, earthy and dull white varieties as agaric mineral, rock-milk, rock-meal, &c. -- these form a transition to marls, chalk, &c.

Encyclopaedia Britannica, 11th Edition, Volume 4, Part 4 "Bulgaria" to "Calgary" Various

It makes by its erosion not only rock-meal, but also large

The Lake of the Sky Lake Tahoe in the High Sierras of California and Nevada, its History, Indians, Discovery by Frémont, Legendary Lore, Various Namings, Physical Characteristics, Glacial Phenomena, Geology, Single Outlet, Automobile Routes, Historic Towns, Early Mining Excitements, Steamer Ride, Mineral Springs, Mountain and Lake Resorts, Trail and Camping Out Trips, Summer Residences, Fishing, Hunting, Flowers, Birds, Animals, Trees, and Chaparral, with a Full Account of the Tahoe National Forest, the Public Use of the Water of Lake Tahoe and Much Other Interesting Matter George Wharton James 1890

Toward the end of the ice period, while its Hoffman companion continued to grind rock-meal for coming plants, the main trunk became torpid, and vanished, exposing wide areas of rolling rock-waves and glistening pavements, on whose channelless surface water ran wild and free.

The Yosemite John Muir 1876