Indeed ...
Except crosses dont exist naturaly in the world.

That would be good example for her shoulders and the form on her jewel on forehead ...
You know what i mean right? Comparing shape, to shape.

Onyx on the other hand is just a stone ... a material.

So to make adequate example you would need to say something like:
All Christians wear at least one jewel with Ruby ... therefore if you see someone wearing Ruby, its logical to presume that person is a Christian.
Wich does not work like that.

The fact that Gods can manifest physicaly in this setting seems completely irellevant to me.