Some recent ammonites: before & after

[Shaun-DFW Fossils]

Hello everyone! I recently acquired a Zoic carbide short tip for my dremel 290. I had previously been using a tip from China that worked fine, but its very weak and tougher matrix seemed impenetrable. The new tip is amazing. While the dremel still vibrates and makes more noise than the nicest scribes I’ve used while volunteering at a local university, the new tip gives the dremel enough power that I’d call it a contender with those nicer scribes. 
the one tool I still need to acquire is the air abrasive. Some may cringe at this, but my “alternative” to the abrasive at the moment is a very brief 5-10 second dip in a 50-50 water and muriatic acid mix, immediately counteracted by a rinse and covering with baking soda. I tend to not use acid as much on fossils covered with calcite on the exterior, like the nicer woodbine ammonites, as it can dissolve very quickly in my experience. 
here are a few “before” pics of mortoniceras ammonites from the duck creek and Fort Worth formations, and one small nautiloid from the Grayson. By the way, the first ammonite was particularly difficult because of how erosion impacted the matrix and the fossil, which seemed almost indistinguishable near the larger end. I risked going too deep but eventually worked off the actual matrix. Lots of white calcite crystal is visible on it, very nice sutures, too.

And after:

[Jaybot]

Nice prep work!  Is that last pic of a shark tooth embedded in the ammo?

 

[Ludwigia]

Very good! I'm just wondering how much difference an air abrader would make on this material, since it looks to me like the matrix has pretty well the same hardness as the fossils. Or am I wrong there?

[Shaun-DFW Fossils]

7 hours ago, Jaybot said:

Nice prep work!  Is that last pic of a shark tooth embedded in the ammo?

 

Thanks Jay! Yes, one of two ammonites I have (that I’m aware of) containing embedded teeth. Pretty remarkable what settled onto these critters!

I attached pics of the opposite side of the ammonite featuring the tooth and also under UV light:

[Shaun-DFW Fossils]

4 hours ago, Ludwigia said:

Very good! I'm just wondering how much difference an air abrader would make on this material, since it looks to me like the matrix has pretty well the same hardness as the fossils. Or am I wrong there?

Thank you Ludwigia! The abrader (when used carefully) typically blasts off matrix from the fossil, even with the softer limestone material, so they are just different enough to achieve the desired effect. But too much pressure or too close and it can definitely damage the fossil. The woodbine ammonites seem to be typically the easiest to prep, the mortoniceras can vary.

[Shaun-DFW Fossils]

Random addition: “yin and yang” duck creek mortoniceras ammonites from a creek near Justin, Texas. I wanted to remove the ammonite but my wife wanted me to leave them together. I sawed the bottom flat, so it naturally stands up or I can lay it down like a record player. She was right about the better look. And no, she’s not reading this…