. Besides
from those coming from Centennial Mine, the Isle Royale Mine just south
of Houghton, seems to be only one I'm sure that produced "well-greened"
(no bluish tint) datolites due to the weathering of very minute copper
inclusions by ancient brines. The interesting thing about those datolites
from Isle Royale mine is that they're like sponges, soaking up water and
as a result, their colors intensified. The datolites from that mine may
be most greenish of any datolites found so far and I mean green color without
blue tint. Most datolites from Isle Royale are white and some came with
black to gray copper inclusions and I have seen few datolites with turquoise
hues. Several times, this mine dump had been bulldozed several times and
I don't know if any more datolites still can be found since I haven't visited
the place.
Click on to see larger map.
Turquoise color intensifies when wet.
Typical datolites with gray copper inclusions
Most greenish datolites(without bluish tint) I have seen so far.
