Specular iron ore occurs in the form of brilliant metallic scales on many lavas, as at Vesuvius and Etna, in the Auvergne and the Eifel, and notably in the Island of Ascension, where the mineral forms beautiful tabular crystals.
The output of iron ore has greatly increased; in1870-1880it averaged annually little more than one-quarter of the amount in 1902.
Lead ores (chiefly argentiferous galena) and building stone are found, and iron ore is distributed over the hilly country.
Impurities.-The properties of iron and steel, like those of most of the metals, are profoundly influenced by the presence of small and sometimes extremely small quantities of certain impurities, of which the most important are phosphorus and sulphur, the former derived chiefly from apatite (phosphate of lime) and other minerals which accompany the iron ore itself, the latter from the pyrite found not only in most iron ores but in nearly all coal and coke.
Coal, textiles and iron and steel goods figure prominently amongst the imports, and emery, leather, lemons, sponges, flour, valonia and iron ore amongst the exports.
In the Tertiary region are found small quantities of iron ore and an indifferent brown coal.
For coal, iron ore and other cheap minerals, mechanical handling by many different methods is used in loading and unloading railway wagons and vessels, and in forming the stock-piles and reloading the mineral therefrom.
There is lignite in the Dongola mudiria and iron ore is found in Darfur, southern Kordofan and in the Bahr-el-Ghazal.
Vessels go to Porman to land coke and coal, and to load iron ore and lead.
The yield of iron ore is almost one million tons annually, while gold, silver, tin, graphite and salt are also mined.