On the occurrence of Beekite in connection with "fossil organic remains" in New South Wales
Abstract
Among the many mineral substances replacing the original carbonate of lime composing what are generally known under the name of "fossils," are iron-pyrites, iron-oxide, sulphur, malachite, magnesite, talc, and silica of various forms, such as Beekite, chalcedony, and both common and precious opal. By far the commonest mode of replacement is that whereby an originally calcareous skeleton is replaced by silica. This process of "silicification" – of the replacement of lime by silica – is not only an extremely common one, but is also a readily intelligible one; since carbonate of lime is an easily and flint a hardly soluble substance. It is thus easy to understand that originally calcareous fossils, such as the shells of Mollusca, or the skeletons of Corals, should have in many cases suffered this change, long after their burial in the rock, their carbonate of lime being dissolved away, particle by particle, and replaced by precipitated silica, as they were subjected to percolation by heated or alkaline waters holding silica in solution.
