Friable rock.
Indurated earth liable to be disintegrated by atmospheric influences.
Decomposed rock.
Rotten decomposed rock.
Or any mass of earth cemented together by a substance, weather-resisting or not, requiring blasting or that can be excavated by means of bars and picks.
The slope of repose required may range from overhanging or vertical to that of the earth of which it consists when disintegrated and dissolved; therefore the angle of repose varies considerably, but the following cardinal principles may be followed without fear under ordinary circumstances and conditions.
Granite. Quartz, if not fissured, and when little mica is present in it, and most of the igneous rocks,
Overhanging, vertical, to ⅛ to 1.
Also porphyry, gneiss, trap, but their stability varies considerably.
Compact hard sandstone and limestone and other solid sedimentary rocks producing stone sufficiently hard and weather-resisting that it can be used in construction,