Why the two different Jurassic/Fossil dials?

[miamiclay]

I’ve noticed that the Fossil/Jurassic Park Day-Date dials seem to come in two distinct colors; I’ll call these Jurassic and Jurassic Dark.

At first, I thought the Jurassic Darks were actually Ammonite dials (and indeed some of them are described by sellers as Ammonite), but I don’t think that’s correct. The tiny-circle patterns of the Jurassic Darks are different from the Ammonite dials, but identical to the patterns in the Jurassics. I feel sure it’s not due to lighting or the other vagaries of rendering photos on screens. It seems the text on Jurassic dials is always black, and the text on Jurassic Dark dials is always gold.

Most critically, there doesn’t seem to be any spectrum *in between* these two shades - Each dial is pretty clearly one type or the other.

Photo of each are below - Does anyone know what’s the story here?
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[77T]

I believe you’re seeing the variations in calcite that formed 200 million years ago.

The lighter version comes from formations in sandy sediment and the darker from muddy sediment.

Calcite is often primarily from tiny shells of marine organisms, e.g., plankton and baby bivalves. So the little circles are actually cutaway cross sections of the petrified tiny creatures.

Also think they got their name “Jurassic” from the period in which the calcite formed. Jurassic spanned from the end of the Triassic Period 200 million years ago to the beginning of the Cretaceous Period 145 million years ago.


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[miamiclay]

Originally Posted by 77T

I believe you’re seeing the variations in calcite that formed 200 million years ago.
...
Also think they got their name “Jurassic” from the period in which the calcite formed.

Thanks!

I think Rolex only ever called these “Fossil” dials, and their “Jurassic Park” nickname just arose in the public because of the movies.

Sandy- vs. muddy-sediment fossils make sense, but if that’s all it is, I’d expect there to be a smoother variation in color, a range rather than just the two distinct types.

It certainly could be a very simple explanation - E.g., Rolex only bought two large chunks of fossil, from which all these dials were made, and one chunk was simply darker. Maybe one color is earlier and one later? (Both are usually marked Swiss Made, but I’ve also seen T Swiss Made T, and just Swiss.) I don’t know whether Rolex itself disclosed what epoch the fossils are from, presumably they could be earlier than Jurassic, even earlier than the entire Mesozoic.

But, given Rolex’s longstanding obsession with QC and consistency, it still seems unusual to me that there are these two clear (but never acknowledged) types of a fairly recent dial - I believe Rolex at some point advertised that “only one of every thousand” dial blanks in certain materials passes their QC. They look so different, and they even have different colors of text according to which color fossil they are.

I have not yet tried to compare dates or serial numbers, to see if that is the dividing factor - Unless someone here knows, maybe that’s the next step ...

[77T]

It’s really much simpler in my opinion. The reason for the 1 in a 1,000 claim is that Rolex chose to have a light dial and a dark dial. Using 2 color swatches chosen by the dial designer (remember these were produced by subcontractors) sample blanks were accepted or rejected based upon their fidelity to the color swatch. Ergo the uniformity. In truth, calcites come in a wide range of colors.

Sourcing fossilized calcite from quartz bearing limestone yields the lighter colors. Other rocks with an high iron content yields reddish browns.

From my reading, these specimens only came from a narrow 50 million year period between Triassic & Cretaceous Periods. AKA Jurassic period of the Mesozoic Era. Conditions didn’t exist in other eras to produce these unusual creations.




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