The shell rock — a natural stone white, is more often than dairy color at the heart of which strong armors and sinks of sea inhabitants. The solid age of breed contains more than 550 million years. The main places of its adjournment — layers of the Devonian, coal and Jurassic periods. Big dobyvny pits of a shell rock are on the Crimean peninsula, there is a stone also in the territory of Azerbaijan, Dagestan, Kyrgyzstan, Ukraine.
It is necessary to estimate visually each stone on existence of an open time, and still to pay attention to weight of limestone - the copy weighing not less than 16 kg as it differs in rather dense structure and small porosity will approach. You should not neglect careful studying of the certificate of quality of a meterial.
The most certain way to estimate shell rock density — with a force to knock the stone about a firm surface. Quantity of pieces on which the mineral after blow will scatter objectively confirm its qualities. So, no more than three broken parts indicate a dense shell rock of the M-25 brand. The stone of the M-35 brand cannot be broken thus in general. The more density of natural material, the is less than pieces and sand it will turn out as a result of blow.