The importance of colour or the absence of it

When collecting fossils, especially in a beach environment like the Yorkshire coast, where you often have to deal with a huge variety of different rocks from different layers, sometimes intermixed with all sorts of glacial drift, recognizing the fine differences of colours of the rocks is of some importance – it helps you pick out the rocks that (from experience) most likely contain fossils, even if they don´t show on the outside. For example when you´re red/green colour blind you´ll have more difficulty picking out subtle greenish shades of some lower liassic rocks.

Rock colours on the beach, a toarcian mudstone in the middle

Rock colours on the beach, a toarcian mudstone in the middle

As a collector I find colour equally important in identifying fossils and judging their provenance. Consider these two ammonites :
Two ammonites in black & white

Two ammonites in black & white

Of course I tricked you here : I intentionally converted the photographs of the two ammonites to black and white, even then I had to modify the exposure of the second picture somewhat to make it look more than the first one.
Here is what they really look like :
Two ammonites, natural colour

Two ammonites, natural colour

What a difference ! The left ammonite looks very much like a Yorkshire one now, while the right ammonite which is preserved in a strikingly light grey marl is actually from near Cingoli, Italy (specimen swapped against some Yorkshire material with an Italian member of the UKFOSSILS forum – thanks again !).
I guess one of the main reasons why many professional palaeontologists in their publications almost exclusively use greyscale photographs is just that : It eliminates colour variations. Sometimes fossils are even coated in white ammonium chloride smoke to further eliminate potential reflections, translucency, and greatly enhace surface detail.
This way you make specimen more comparable with ones from other areas, removing the unwanted effects of colour due to different preservation.
Other reasons may include the relative simplicity of the B/W photographic process compared to colour and the past cost of colour printing.
Now are the photographs in my book going to be black and white ? No – this is not going to be a book fulfilling all scientific standards, I want to show colour differences, I want to show you what the matrix in the luridum subzone looks like compared to the maculatum subzone, the golden shine of a pyrite ammonite, the deep black of a Gagaticeras´shell, or the chocolate-brown of a Yorkshire Zugodactylites. While the effects of whitening the fossils using ammonium chloride can have a dramatic effect on visibility of detail, it adds huge complexity due to necessity of a lab. Digital photography has eliminated many difficulties in the colour process (and printing in colour is not as cost-prohibitive as it used to be), but it has brought new ones as well – more on that later…
AndyS
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2 Comments

  1. Adrian

     /  June 10, 2012

    Good for you Andy, I think your reasons stated earlier about your book,pitched inbetween being too scientific and above begginers level if you like is spot on!.
    Now you raise a topic that really affects me,colourblindness.
    I am colour blind and find it really difficult to tell some of the different matrixes apart,even after many fossiling trips out with you and looking at what you pick up.
    I still rely on other indicators,such as the exposed sides of an ammonite or the shelly matrix that might contain amalthus.
    Taking photo’s of ammonites in their natural colours will just enhance your work in my opinion.

    Adrian

    Reply

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