At Ruby Hill near Bingara they were found in a breccia filling a volcanic pipe.
In this part of its course the rocky sides of the valley, which sometimes closely approach the river, are composed of marls and gypsum, with occasional selenite, overlaid with sandstone, with a topping of breccia or conglomerate, and rise at places to a height of 200 ft.
Breccia, Il Diritto dinastico nelle monarchie dei successors d'Alessandro Magno (1903).
Sandstones, quartzites, conglomerates and breccia make up the formation.
Its roof is a single flat stratum of limestone; its walls are well marked by lines of stratification; dripstone also partly covers the walls, fills a deep fissure at the end of the cave, and spreads over the floor, where it mingles with an ancient bed of ashes, forming an ash-breccia (mostly firm and solid) that encloses fragments of sandstone, flint spalls, flint implements, charcoal and bones.
A deposit of sinter and a calcareous sandstone, known as the Kalahari Kalk, considered by Dr Passarge to be of Miocene age, overlies a sandstone and curious breccia (Botletle Schnichten).
West Elk breccia 3000 ft.
There has been much contirversy concerning the nature and origin of the blue ground itself; and even granted that (as is generally believed) the blue ground is a much serpentinized volcanic breccia consisting originally of an olivine-bronzite-biotite rock (the so-called kimberlite), it contains so many rounded and angular fragments of various rocks and minerals that it is difficult to say which of them may have belonged to the original rock, and whether any were formed in situ, or were brought upfrom below as inclusions.
Cohen, who regarded the pipes as of the nature of a mud volcano, and the blue ground as a kimberlite breccia altered by hydrothermal action, thought that the diamond and accompanying minerals had been brought up from deep-seated crystalline schists.
Red granite was obtained from the First Cataract, breccia and diorite were quarried from very early times in the Wadi Hammamat, on the road from Coptos to the Red Sea, and porphyry was brought, chiefly in Roman times but also in the prehistoric age, from the same region at Jebel Dokhn.
The greater part of the surface is composed of a volcanic breccia, with here and there lava-streams exposed in ravines, and sometimes on the surface.
Among the Griquatown series of quartzites, limestones and shales are numerous bands of jasper and large quantities of crocidolite (a fibrous amphibole); while at Blink Klip a curious breccia, over 200 ft.
(4) Filling the bottom of the cave was a hard breccia, with the remains of bears and flint implements, the latter in the main ruder than those found above; in some places it was no less than 12 ft.
All over Iceland, in both the basalt and breccia formations, there occur small intrusive beds and dikes of liparite, and as this rock is of a lighter colour than the basalt, it is visible from a distance.
It is, however, now more generally believed that it exists in the breccia of some of the valleys on the west side of the lake, which is washed into the sea and submerged, till the small stones by which it is sunk are loosened and fall out, when the bitumen rises to the surface.