We apply the term stalagmitic pipes to morphologically atypical speleothems that consist of pipes that are a few centimeters to 3 m long and with walls 1-2 cm thick. They are developed from and in cataclastic sand, made up exclusively of dolomite, present in certain sectors of the cave known as Cueva del Agua (Iznalloz, southern Spain). The cataclastic character of the dolomite sand, with its high porosity and permeability, leads to the development of this unusual morphology as a result of the dispersing mechanical effect of water dripping from the roof of the cave. The high Ca (super 2+) /Mg (super 2+) ratio of the water is responsible for the cementing of the dolomitic sand grains forming the speleothems. This chemistry is also responsible for dedolomitization of the dolomite sand grains. Scalenohedral calcite cement is found in some pores and covers the inner surfaces of the speleothems.