Lapidaryforum.net
Let's Rock => Identifications of Materials => Topic started by: vitzitziltecpatl on May 03, 2016, 07:41:40 PM
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We have three small slices of an estate sale piece, and can't ID the black. Not Hematite or Magnetite. Black on the wheels as it's ground away, and looks like it has crystal faces in it reflecting the light when turned in hand.
I know I'll feel dumb when you guys ID it, but I'm having a mental rock-block here.
Huh. Feel dumb already. Didn't realize I forgot to attach a pic until Robin told me... .
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are the sparkly portions generally more cubic than linear? It looks like a hematitic quartzite with green epidote and white chert. Essentially a sedimentary jasper due to metamorphosis of sea bottom near tectonic vents. Quite common up north and at times has problems with different hardnesses. It would be manganese and iron in the black and specular hematite as the sparkly part.The epidote is a marker of how deep in the subduction trench the rock had been, quite deep.
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There are a couple of larger squarish areas in the black with the look of crystal faces. Lots of small sparkly bits in there too. Some differences in hardness. Didn't suspect Epidote for the green.
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i sent this to you.
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its from around tillamook (bay area not river) oregon or deschutes
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Hmmm - sorry Phish. Must've been a different parcel from the slabs with the "fish-egg" rock. This piece here was a chunk I sliced into three little slabs here recently. Didn't remember you sending that chunk. My apologies, and thanks for the ID.
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My piece
(http://uploads.tapatalk-cdn.com/20160507/464ad1fb64b63a654350ff43f7639b51.jpg)
(http://uploads.tapatalk-cdn.com/20160507/81e907ebe61645c9964161615af3e3bf.jpg)
Sent from my C6916 using Tapatalk
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Hey, Phish, know you've been really busy (understatement - just a little?) so I hadn't replied sooner. Do recall us getting a rock with Tillamook mentioned as the source. That stuck with me 'cuz we buy Tillamook brand cheese and ice cream. When we got that rock Robin and I said it was cool to have something from there. Thanks again.
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That also looks like a epidote -iron quartzite. I saw a translucent piece years ago that was 4 feet thick and over ten feet long and fulls of swirls of pink and yellow garnet and hundreds of perfect pyrite cubes. It sadly washed away in a storm. Keeps your eyes open as there are lots of variations. A warning on this rough -The exterior can get a milky white opaque cast to it from hitting other rocks while the center is very clear and full of surprises. As these pieces tend to be rather large and tough it can make high grading very difficult.