Somebody requested ammolite, so we’re gonna look at some ammolite!
I have here this fossil ammoNite (a species of cephalopod that went extinct about 66 million years ago), which is covered in a thin layer of ammoLite (a colorful and gemmy form of iridescent aragonite found only in the fossilized shells of ammonites). Because it comes from a (previously) living creature, ammolite is classified as an organic gemstone, like amber and pearl!
The ridges of the shell! With how brightly it shines, the ammolite growing atop them almost looks metallic. But it’s not a metal! This metallic iridescence comes from tiny plates of aragonite bouncing the light around. They’re way too small for my microscope to see!
Where did this aragonite come from? The animal made it! Aragonite is what nacre, aka mother-of-pearl is made of. If you’ve ever seen an iridescent seashell, it has this same crystal structure!
There are many chips and cracks in this piece. I guess nobody looks pristine at 66 million years old! As you can see, the ammolite forms a paper thin layer atop the fossil, and inside is just normal stone.
Here, some tiny scratches have worn away some of the iridescence. Because the ammolite is just a thin layer, it can easily chip off. This is why ammolite specimens are usually coated in resin for protection. This piece is untreated, so I have to be careful with it!
Isn’t it amazing? Ammolite on an ammonite!
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