The iron which forms the greatest mineral resource of Alsace-Lorraine is a part of the _minette_ district, about forty miles in length and fourteen miles in breadth, lying on the borders of France and Luxemburg. The Franco-German frontier of 1871 divided this area nearly equally between the two countries, save for a small strip on the north extending beyond the Luxemburg line. Most of this ore is strongly phosphoric (_minette_), and could not be worked advantageously until the invention in 1878 of the Thomas process for dephosphorization. The ores are not relatively rich, the average iron content being 33 to 35 per cent; but they are easily mined and are sufficiently porous to be easily crushed, while a limestone which fluxes easily occurs either with the ore, as at Briey, or in the immediate neighborhood. In 1913 German Lorraine produced 20,600,000 long tons, or three-fourths of the iron mined in Germany. French Lorraine in the same year produced 19,400,000 tons, or 90 per cent of the product of France, of which a considerable portion was exported to Germany. Of the world’s total production of iron in 1913, 29 per cent came from the _minette_ district, i. e., 12 per cent from German Lorraine, 12 per cent from French Lorraine and 5 per cent from Luxemburg. The rest of Europe furnished 24 per cent. The reserves have been estimated as 3000 million tons for French Lorraine and 1830 million tons for German Lorraine; more recent estimates make the two more nearly equal, but with the preponderance in favor of the French. The whole constitutes by far the richest iron supply in Europe and one of the three or four greatest in the world.