What type of adhesive to use?

I bought a fossil (ammonite, cut in half vertically, so you can see the chambers).  I want to hang both halves on the wall.

I bought a 'hinged eye' with a plastic mounting plate, but I have been unable to attach this to the backside (which has some kind of filler in the center).  I have tried SuperGlue (does not adhere to the filler), and I have tried a silicone based caulk (does not grip the plastic mounting plate).

Plan B would be to bend steel wire so that it stretches across the back, and grips on the edge, but that would be visible from the front.

Any suggestions?

Try bondo 

Having a difficult time visualizing this. A few pics would be helpful.

Try hot glue.

How big? How heavy? Any attachment points that would allow it to be mounted on a decorative board? That board could then be fixed to a wall much more easily. I don’t know if you’d want to make anything like a screw hole in an unseen place though.

Another option would be to mount a platform on the wall it would sit upon. 

Any chance for a piece of [what? heavy paper? or?] that would adhere to both the Super Glue and the caulk, inserted between the filler and the plate?  Or a little shelf/platform, per PeterWick....

How about something like this plate hook? 

(The image shows the back)

Apollo_T said:

Try hot glue.

+1

Jaytee said:

Try bondo 

None of the Bondo formulations mention plastic.  I checked with 3M, and they told me that none of their products will work.

jimmurphy said:

How about something like this plate hook? 

(The image shows the back)

This was my original plan.  Problem is that the fossil is too thick and has uneven backside, so the plate hangers won't work.

Here is photo (from the back, front is smooth).  They probably weigh about 1.1/2-2 lbs each.

You can see the plastic/hinged eye on one (but the caulk did not hold).  I wanted the hinge, so the fossils would hang close to vertical on the wall, but if adhesives won't adhere to the plastic, I might have to go to a straight metal eye.

tomcat said:

This was my original plan.  Problem is that the fossil is too thick and has uneven backside, so the plate hangers won't work.

Couldn't you buy one for a larger diameter plate and then bend the plate hanger to conform to the curved back?

tomcat said:

Here is photo (from the back, front is smooth).  They probably weigh about 1.1/2-2 lbs each.

You can see the plastic/hinged eye on one (but the caulk did not hold).  I wanted the hinge, so the fossils would hang close to vertical on the wall, but if adhesives won't adhere to the plastic, I might have to go to a straight metal eye.

what about the double sided tape? I have one that will stick to anything, commercial grade. We use it for gluing hand rails to walls. It’s fierce. 
Another suggestion, clean off all that silicone or whatever glue you used, then clean it with alcohol, then sand it. Maybe those two part epoxy glues would work? 
those are pretty heavy.

Would mounting them on metal stick-ish things on a dark base work? Sort of like the fossil is a lollipop. 

What about a shadow box? They come in different depths and some have clear shelves inside to place items on for display.