The geography and geology of south-eastern Egypt

by John Ball

Viewed as a whole, the granites of South-Eastern Egypt are characterised by their strongly acid composition. Though perfectly normal granites are found in many places, and a gradual passage into quartz-syenite may be occasionally traced, yet on the whole the rocks approximate to the aplitic and pegmatitic types in which quartz and felspar are associated with very small quantities of ferro-magnesian minerals.

We may consider the granites as falling mainly into the following classes:—

1. Normal pink granite.

2. Red pegmatitic granite.

3. Aplite.

4. Biotite-granite.

5. Muscovite-granite.

6. Hornblende-granite.

Ball.—Geography & Geology of South-Eastern Egypt.

PLATE XXII.

ACID IGNEOUS ROCKS.