Kettle Point: Mars Black from Pyrite Nodules

This is one of the very unique places I have been looking forward to visiting for this project. Kettle Point takes it’s name from the round boulders, or “kettles”, that emerge from the underlying Devonian shale beds of Lake Huron. These natural wonders are actually concrentrations of calcite crystals which grew over many centuries around a nucleus of marcasite. Such formations are unique for this area and are not found anywhere else in all of Canada.

But when Reiner, Maggie and I traveled there we weren’t looking for the calcite kettles. There are other smaller formations also at this point which I am hoping will be useful as pigment. These nodules only grow to about 2 inches in diameter but instead of calcite crystals, these are made of pyrite (iron sulfide – FeS2).

The lake at this location is shallow for a long way out and so we walked out into the water looking for small spheres. After a while, I began to worry that this trip might not be a great success; the water’s gentle waves made viewing the floor a somewhat dizzying experience and after the first hour we had only collected a single specimen. But we continued on, hoping for more.

Then suddenly we found a couple more; then more still; until we found a spot where the little spheres of pyrite appeared like gravel. Our little tin bucket began to fill and one property of these little nodules characteristics became very apparent: They are heavy! Even when picking them from the lake’s floor, you knew as soon as you touched a rock whether it was, in fact, pyrite because of it’s weight. In the end, with our bucket full and a little deformed by the weight, I happily slogged it back to shore.

My pyrite nodules aren’t much to look at presently, but I’m hopeful that they will be very useful.

In researching pyrite I’ve come up with a few interesting facts about using this mineral as a pigment: Naturally, iron pyrite is a brown colour and it has been identified in the paintings of the Italian Renaissance painter Frà Bartolomeo (+1517 AD).  Iron sulfate is also mentioned in G. Terry’s  1893 book, Pigments, Paint and Painting, A Practical Book for Practical Men as a source of iron black if roasted.
I’m hoping that I will also be able to coax more colours out of this mineral, but we’ll have to see what my experiments yield.
As much as I think the spherical nodules collected at Kettle Point are wonderful simply in their circular outline, what is inside is even more interesting: The metallic luster and brass-yellow hue of this, “fool’s gold”.  If you look carefully in the photo at the top of this post, you can see that such samples have two distinct layers.  Around the outside of each nodule is the crystalized form, while in the heart each exhibits the mineral.  Regardless of the structure taken, this location yields very pure samples of such pyrite, and I am looking forward to experimenting and creating colour from it.
I am very happy to report that I had some immediate (although unexpected) success with the pyrite nodules collected from Kettle Point: I had created Mars Black!

Mars pigments are a group of synthetically produced iron oxide colours which can range from yellow-red-violet-black. They represent a purer form of the same material that gives colour to the ochre pigments because they don’t have any clays associated with them. Because of this purity, they are also typically brighter and more opaque.

This is very exciting for me, but wholly unexpected. After I had finished calcifying a sample of the pyrite I opened the crucible and saw that the whole mass had turned black. I thought it was ruined! I’m not sure what possessed me to put a magnet to the mass. Pyrite is not magnetic at all, but perhaps inspiration whispered in my ear …

Once the magnet got close enough, the whole mass of black powder jumped around it and formed a mane around it’s head. Then I suddenly realized that I had created the mineral magnetite, or in pigment lingo, Mars Black.

So why are they called, ‘Mars’ colours? The whole group of these pigments comes out of the eighteenth century and today we take the title Mars from the latin, martius, which orginally described this pigment. To the alchemist, Mars symbolised iron; what could be more appropriate to describe this group of pigments?


3 thoughts on “Kettle Point: Mars Black from Pyrite Nodules”

  1. Hello Aaron,

    I wish that the linguistics were genuine material-wise but fool’s gold was nicknamed thus because of its colour and weight tricking the uninitiated into thinking it was something valuable. Any form of metallic leaf is made from soft metals such as gold, silver and copper and, although called “fool’s gold”, pyrite is in fact iron sulfide. Iron is hard and quite brittle so it would crack, rather than spread-out, if I hit it with a hammer. Metal-leaf from this source just isn’t possible, I’m afraid.

    I am still hoping that I might find something I can use for a metal leaf background, but within the area I am working these rocks are very rare and only exist on the off-chance that a glacier dropped off a sample with its retreat during the last ice age. But who knows, something might come …

    I hope this answer is helpful. Thanks for your question.

  2. I was out in Ohio last year & found a few of them spheres at first I thought it was gold but then the more I looked at it I knew it wasn’t because of the hard ness of it & the sharp corners it what ever well they are nice to put with my agate collection


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