u/GhostsinGlass

I apologize some of the macro attempts are blurry, the minerals are interesting.

I found this sitting in the dirt beside the sidewalk here in Thunder Bay, Ontario. It had an odd shape and felt oddly heavy so I thought I would cut it. It was nicely encased in clay and iron oxide.

There is a picture from the original cut before I polished it included.

It is not magnetic, scratching with a nail is all over the place in hardness, even among areas that look the same. The colour is amazingly black depending on the angle the light hits it.

I have not seen any rock around here quite like this in my time cutting and polishing them. Some form of diabase, or gabbro, or diorite is all the guesses so far.

Thanks for any help.

Edit: Askgeology helped narrow it down, it's gabbro that evolved into Amhobofite, or Amphibolite, or something. Twas used a long time ago by a guy named Logan Sills as road filler underneath old streets, so those who said asphalt were close by proxomity. 10 Points for the Civil Engineers in the room.

I assume this is as good as the polish will get given the high amount of various crystals within.

Still not exactly sure what it is. Have never seen a unit like this around the northwestern shore of Superior. A diabase or gabbro or diotite something or other. I've seen someone mention black amethyst but I don't believe it to be such.

Sounds like an industrial unit

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Slabbed or shaved.

Or it could be a vertical flat lap, hmm.

Think those Amazon flap disc peddlars would sponsor that?

Hopefully Reddit lets me post the shrunken version. 16927x was too big.

I thought they were small splitshot lead sinkers from someones tackle box but they don't look like any I have ever used.

Not a fan of this rock but a guy reached out on Reddit, said his daughter thought she had a geode for sure and was looking for someone to cut it open. Trying to turn that dissapointment into something special.

Last piece to add I am going to try and grind a slab razor thin so the light shines through any transparent/semi-transparent inclusions then encase it in resin.

Do not attempt if you do not have a lathe capable of going slow and cannot find a center properly.

Even with the lathe going slow and only using small discs the slug will still be doing Mach 3 Gillette speeds.

Pardon my workbench. I have HGTV and it gets messy when I putter.

Absolute fuckhead behaviour.