Sentence:  During my stay at Kamalia there was a smelting furnace at a short distance from the hut where I lodged, and the owner and his workmen made no secret about the manner of conducting the operation, and readily allowed me to examine the furnace, and assist them in breaking the <WSD>ironstone</WSD>. 
Meaning of the word marked with <WSD> tags:  Any ore of iron which is impure through the admixture of silica or clay.