Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/107

 short distance from the joints, the best stones being found in the latter position, where they usually occur (more especially the larger ones) in the centre of small red marly or ochreous nodules. Those in the open joints are generally dull and white, or at the best of a pale-blue tint ; and as a general rule it may be said that the redder the rock the finer will be the colour of the turquoises it contains. These conditions of occurrence, although they can only be taken as applying to the rock as now exposed, probably are generally similar to those that governed the explorations of the ancients, as we see everywhere large areas (say from 30 to 40 yards square) excavated with only the smallest of pillars, and these very often much undercut, with occasionally a kind of level or stope along the course of a crack, where a nest of mineral was probably found. The general system of working appears, therefore, to have been pretty much the same as that now adopted by the Arabs, namely, to follow the joints, removing the rock adjoining the side, which is then broken small and sifted through a sieve of about half-inch mesh. The whole of the coarser fragments kept back are then taken to the mouth of the cave, where they are carefully picked over in daylight. The likely- looking nodular pieces are rubbed down on a piece of rough grit, in order to see whether they contain turquoises or not ; and if any blue colour is made apparent by this treatment, the stone is considered to be worth keeping.

Since the mines were abandoned by the late Major Macdonald in 1865, no regular operations of any consequence have been carried on, the latest having been undertaken by a Frenchman, about two years since, in the lower caves of Wady Sidreh. It is said that he made a successful venture. The principle adopted in working was to provide the Arabs with tools and powder, paying a small daily wage in addition. The turquoises produced were then purchased at a rate agreed upon beforehand. A somewhat similar system was followed by Major Macdonald ; and it is no doubt a fair arrangement for both sides, having regard to the inhospitable nature of the country, which is such as to prevent the introduction of foreign miners ; but unfortunately it is not easy to be sure of getting the whole of the produce, as the larger and more valuable stones command a ready sale in Egypt, and are often kept back, only the smaller and inferior ones being handed over to the person providing the means of working.

Old Mining-tools. — The ancient workings in Wady Maghara, although much encumbered by cliff-falls at the outside, are for the most part accessible for a considerable distance from the surface, and in many instances the old faces of work may be seen. These are covered with small and irregular tool-marks, of such a character as to leave no doubt that they have been made with flint flakes, great numbers of which are found strewing the valleys and hill- sides, as well as within the workings themselves. Most of these flakes are of a triangular or trapeziform section, brought up to a point, which is generally well worn and rounded, and the shape of which, when blunted, corresponds perfectly with the grooves on the face of the rock. In

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