Page:A treatise on diamonds and precious stones including their history Natural and commercial.djvu/71

 stitute the alluvium, they are considered good indications. In one part of the Diamond District the cascalho forms a solid breccia, cementation having taken place from the oxidation of the iron: in this mass Diamonds and gold are sometimes found enveloped.

To explain in a more particular manner the general locality of the Diamond, I will suppose a valley to be formed by mountains of granite; through which runsa rivulet, having on its margin gradually rising hillocks or plains, more or less distant from the base of the mountains. It is by analogy that the presence of the precious gem in such a situation is to be inferred, and hence a little geological experience is highly necessary. Diamonds having been found in ravines, formed by such