and
moisture of their surroundings ; alumina, as well as the oxides of
copper, manganese -and iron, are often washed across and over these
bones lying on the cave floor, so that in time, this silt acts on the
substance of the bones, forming a variety of turquoise of exactly the
same composition as that just described, and of the same colour. So
that around the bones there eventually appears a beautiful turquoise
casing ; the bone centre is also coloured like its casing, though not
entirely losing its bony characteristics, so that it really forms a
kind of ossified turquoise, surrounded by real turquoise, and this is
called the " bone turquoise " or " odontolite"
