Ammonites From The Bear Paw

[John K]

My son got busy over the summer with work and other things, so I took over the prep of a cluster of ammonites he was working on that he found last year in Montana on one of our fossil safari's:

I'm working with a $20.00 Dremmel engraver, pretty much exclusively. I got a little rambunctious and broke off the back shell, but I glued back on with superglue and it seems to be stable. Otherwise, it's going slow, slow slow - that black shale is hard.

Question - the front of the group is covered with a thick crust of what looks like calcite. I'd like to use an acid like vinegar to take it off, but am afraid of messing up the existing (and beautiful, I may add) mother of pearl of the ammonites... is this something to worry about? Or do I need to take it off mechanically?

Edited August 29, 2015 by John K

[PFOOLEY]

I can't help, but you had me at "Bear Paw"...some of the best in the world.

[Ludwigia]

I wouldn't even attempt it. Mother of pearl, or nacre, is either still in its original substance aragonite or else converted to calcite, both of which are susceptible to any acid. What you need is a good air abrader.

Edited August 29, 2015 by Ludwigia

[John K]

Thanks Roger - that's what I thought. Yeah, an air abrader would be nice to have; maybe some day...

for now I'm "stuck" with the engraver (which actually works better than I expected...)

[Mike Pocock]

Hi,

Ludwigia is correct re the acid I used some on one of my ammonites and destroyed its surface.

However I use a Dremmel on some of my prep work, what I did to help remove hard matrix was the following.

1 Get a set of tungsten darts

2 Remove the body of the dart

3 Remove the engraver bit (small screw on shaft)

4 Place dart tip in slot and replace screw.

I found this to be very effective mainly I think due to the fact that the point of contact is much smaller, I also found that the dart tip was much better for very fine detail in the centre of the swirl, it is also very easy to re sharpen the dart tip with a simple wet stone.

Although I have got to say I have moved on to an air scribe now and its much easer.

Hope this helps

Regards

Mike

Edited August 29, 2015 by Mike Pocock

[RJB]

Yeah, that Bear Paw can be some hard stuff. That 'Crust' is either calcite or barite (spelling?) and it looks like barite to me. Your life would be much easier if you had a ME9100 airscribe, but those are a bit on the expensive side. I do wish you the best of luck.

RB

[John K]

I spent a little bit more time on this cluster of ammonites. I'm also trying to keep a photo record of my progress, however slow it is...

starting out:

an hour in:

an hour or so tonight:

[Ludwigia]

This goes to show that patience really is a virtue...

[RJB]

You've got a lot more patience than I do. Go get em John! Woooooop!!! Wooooop!!!

RB

[John K]

Well, I put another hour or so into this, and was horrified when a big chunk broke off, taking most of the main ammo with it.

I was able to glue it back on (I even found the "horn" that had popped off...) and was pleasantly surprised to see what looks like another whole ammonite peeking out, right under the one that had broke off. A little bit smaller than the other two, but it looks like it's in good shape:

I'm slowly working around the edges of this guy, in addition to the other two. Geez, I thought this was slow going before!

My worry now is that my son is going to want it back if I ever finish...

Edited September 3, 2015 by John K

[Ludwigia]

I could see that third one coming in your first pic. Don't worry. Your son'll probably be going to college when you get that finished