On the bank of the Tiretaine there is a remarkable calcareous spring, the fountain of St Allyre, the copious deposits of which have formed a curious natural bridge over the stream.
Where the flints lie the chalk must have been dissolved away; we have in fact a kind of metasomatic replacement in which a siliceous rock has slowly replaced a calcareous one.
With the exception of the coral and a small amount of calcareous sandstone, the rocks are entirely volcanic and range from basalt to trachyte, but are mainly basalt.
Others that are exceedingly productive are the black calcareous loam of the prairies, the calcareous silt of the bluff belt along the eastern border of the Delta, and the brown loam of the tableland in the central part of the state.
Orifice concealed at the bottom of a vestibular shaft, surrounded by a solid or vesicular calcareous deposit.
It owes its commercial value to the beauty of its hard red calcareous axis which in life is covered by a cortex in which the proximal moieties of the zooids are imbedded.
On the south coast of the same island are coarse-grained, brownish micaceous and light-coloured calcareous sandstone and marls, containing fossils, which render it probable that they are of the same age as the coal-bearing Jurassic rocks of Brora (Scotland) and the Middle Dogger of Yorkshire.
Belong to the third class of Calcareous or Lime Rocks.
Shell largely chitinous, not spiral, its calcareous apex projecting through a small hole in the mantle.
It v e mires very little moisture, grows luxuriantly on the thin calcareous soil of Yucatan and is cultivated almost exclusively by the large landowners.