Many tons of limestone are used each year in Missouri as a soil fertilizer because it neutralizes acidity, coagulates the clay, furnishes calcium to the plants by way of the colloidal clay, and frees other chemical elements so that they become available to the plants. No doubt rocks other than limestone will be crushed and added to the soil in the future, but today our attention is focussed chiefly on limestone and dolomite. The value of a limestone quarry for agricultural purposes depends upon availability, amount of overburden, purity of the stone, ease of crushing, and size of deposit. For instance, a stone of 90% purity, which is close at hand, will probably be more valuable than one of 98% purity which must be hauled fifteen miles. Bare hillsides or creek banks where a crusher can be set up to handle the stone without extra lifting are preferable for quarry sites. Usually the overburden is less in such an exposed face. Impurities in limestone deposits may be large chert (flint) nodules which can be hand-sorted out, sand grains, clay which settled into and onto the stone during its accumulation, and pyrite (fool’s gold) or other minerals of lesser importance. Clay impurities simply act as useless extra weight which must be handled. Sand grains, however, are hard, and will abrade and wear out crushing equipment. Chert and fine-grained silica likewise are harder than steel and will wear a crusher excessively. Pure limestone (calcite or dolomite mineral) has a hardness less than that of steel and will only polish or wear the metal slightly. [Illustration: Typical, intermittently-operated, farm limestone quarry near North Kansas City.] It will probably pay to give some thought to this matter of crushing when selecting a quarry site for agricultural limestone. The several beds of stone available should be tested not only for amount, but kinds of impurities. Samples sent in for testing must be _representative_ of the rocks under consideration or the analytical results are meaningless. The writer does not believe this point can be over-emphasized. Time after time he has seen samples taken of geological deposits for testing which no more represented the deposits than a bantam rooster picked out of a chicken pen would represent the egg-laying or weight-production possibilities of the flock of Plymouth Rock hens.