@rleder, @bdattilo, @bmacfadden, @crobins, @rebecca-freeman, @jkallmeyer
Thanks for everyone’s help.
Using suggestions provided by you and information from other sources, I am creating a set of definitions and rules to help everyone determine if a fossil is a mold or a cast. I am interested in making the definitions and rules better, clearer and easier to use. I need the help of everyone.
Here is what I have:
1. A mold is an imprint of an original fossil.
2. Molds can only be made against an original fossil.
3. A cast is a replica and/or reasonable copy of an original fossil.
4. A cast can only be made against a mold of an original fossil.
5. An original fossil is defined as an organism, fossil, fossil to be or a cast thereof.
6. Trace fossils are various tracks, trails and burrows that give us information about what the original organism did while alive.
7. The surface of a trace fossil created by the original organism against a material is an original fossil when the surface of a trace fossil created by the original organism against a material cannot create a cast of the original organism that created the trace fossil.
8. The surface of a trace fossil created by the original organism against a material is a mold when the surface of a trace fossil created by the original organism against a material can create a cast of the original organism that created the trace fossil.
Here are some related rules or corollaries:
9. An original fossil must exist before the mold of the original fossil.
10. The mold of an original fossil must exist before the cast of the original fossil.
11. A cast of the original fossil cannot be created against the original fossil.
Let’s apply the definitions and rules to an actual situation. Is a filling contained within the original shells of a closed bivalve a mold or a cast? A mold (the infilling) is an imprint of the original fossil (the closed bivalve.) The mold (infilling) can only be made against the original fossil (closed bivalve.) Remember, a cast (replica and/or reasonable copy of an original fossil) can only be made against a mold. The infilling can create a cast (the interior only) of the original closed bivalve. The infilling is not a cast because the infilling is not a replica and/or reasonable copy of an original fossil.
It is important that we agree what the original fossil is first. Then we can determine what are the fossil mold(s) and cast(s). We must also remember that a cast of the original fossil must be a reasonable copy of the original fossil.
I welcome any suggestions, new definitions and rules along with supporting rational arguments and reasoning. Sources for definitions would be helpful.
I am also willing use these definitions and rules to see if a fossil that you describe is a mold, cast or other type of fossil. The more we use these rules and definitions, the better they become.
Once we improve these definitions and rules please use them.
Thanks,
John