Joachim John Monteiro, Angola and the River Congo, vol… (1875)
“ The malachite is often found in large solid blocks;—one resting on two smaller ones weighed together a little over three tons, but it occurs mostly in flat veins without any definite dip or order, swelling sometimes to upwards of two feet in thickness, and much fissured in character from admixture with dark oxide of iron, with which it is often cemented to the clay in which it is contained. ”
