Talc-schists.
Talc-schists, though not widely distributed, are abundant in certain localities. They form the main rock in many of the hills in the district called Um el Huetat, to the west of Gebel Atut in latitude 25°, where there are numerous old mines. In this district there are immense masses of talc-schist of remarkable purity. The rock [10,364] is of a grey to green or brown colour, distinctly schistose, cleaving easily with a soapy feel, and easily scratched by the finger nail; more massive forms occur which can be easily carved into pipes, and these are frequently smoked by the Bedouin. I descended one of the old shafts at Um el Huetat, and found no evidence of other minerals having been worked than the talc itself. A somewhat more earthy variety of talc-schist [10,396] was met with near the Rod el Ligaia. Talc-schists also occur at Gebel Sikait [10,383] and Gebel Zabara, where, as at Um el Huetat, they alternate with mica and hornblende schists. But at Sikait and Zabara the talc-schists are decidedly subordinate to the mica-schist in which the beryls are found.
To the class of talc-schists is also probably best referred a fissile and very rotten purple-brown schist, containing cubes of limonite, which was found near the triangulation station on Gebel Hamida, and again near the old mines of Romit. The microscopic slide of the Romit specimen [12,139] shows the bulk of the rock to consist of talc and chlorite, with blotchy stains and floculent-looking masses of brown iron oxide and occasional clear irregular granules of quartz. In this are plentifully embedded perfect little cubes of limonite. The limonite cubes [12,129 and 12,136] weather out easily from the rotten matrix, and can be gathered from the ground at the foot of the exposed surfaces.