Lapidaryforum.net
Let's Rock => Identifications of Materials => Topic started by: Felicia on February 28, 2020, 01:59:28 PM
-
I have a pretty good idea of what the stone is, though it was bought as an unidentified slab. I was cleaning up the saw marks on the one side, and noticed some hair-fine silvery metallic streaks running through the red and ocher bands. Can't get a good enough photo but have provided a sketch to show their location. Does anyone know what they are. Thanks. [ You are not allowed to view attachments ] [ You are not allowed to view attachments ]
-
It is an iron (maybe Hematite) not sure what the iron is in Owhyee Jasper. It can occur in the center of the striations and would be the agent responsible for the coloring. Be aware with this Jasper that is can also have hairline cracks in that same line and causes a lot of frustration when cutting to have them let loose. Check carefully although they probably are iron stripes a fine crack can have a similar appearance that has had staining go down into the crack. If it is a super piece that you want to cut wet the slab and quickly wipe off the water on your arm and hold up the slab to see where the moisture will give away a lot of cracks but some in this material aren't easy to find. If it were a piece I really wanted to cut I might try to seal along any potential flaws like those lines before trimming and cutting.
-
Thanks. Don't see any difference when wet/drying. The piece is very hard, very smooth and porcelain-like. Hope it doesn't come apart along those lines.
-
Sometimes metal from the blade transfers to the stone. This could be what is going on. Has you tried sanding the surface and see if the metal is just a surface coating or deep?
-
Yes, that's what I was doing when I noticed it. Got it sanded down well, so I can decide what to do with it as far as cabbing goes. Probably a free-form. It's a nice "scene".
-
Those metallic streaks went back to being thin black streaks overnight. Go oxygen.
-
It is funny the similarities between Owhyee and Norenna Jasper sometimes you have to do a double take but with the Norenna being more grey in background and Owhyee tans it helps. Both have the same issues though.
-
With jaspers it is almost always iron with different valences and colors. The metal is a much more reduced form while the yellows are the most oxidized. Concentration is also a factor with blues in reduction being as little as 1%.If that concentration had been deposited in oxidizing conditions you would have straw yellow.
-
I've even got a Lake Superior agate with what looks like an iron inclusion of some sort. Copper is the usual metal inclusion but this is metallic black. It and others are in my bracelet.