Rubble is large, irregular pieces of broken stone used as riprap and in the construction and maintenance of breakwaters, jetties, and rock-fill dams. Generally, rubble is quarried, but in special instances natural boulders are used. The engineering geologist is required to provide the design and estimating engineers with geologic and engineering data on rubble sources to facilitate the design of the structure. Geologic data are concerned with assessing the inherent structural features and durability of the rock, as well as site conditions, quantities, and quarrying characteristics. Engineering data include a plan for operation of the quarry consistent with the contractor’s experience, spoil facilities, transportation, utilities, and a large quarry-test shot to determine fragmentation. Service record of the site rock and those of similar sources are valuable guides in evaluating the rock. Laboratory tests on representative samples are a further means of evaluating a proposed site. The five case histories given of stone from widely separated quarries demonstrate that development of each quarry has specialized problems; methods of exploration cannot be stereotyped and must be tailored for the site; and evaluation of exploration results includes the use of engineering data.