Makes me think of those images of Pyura chilensis that were circulating.
I’m sure it has zero lead contamination…
So I am super intrigued by this, so I deceided to learn a little more. I went over to Wikipedia.
and I found the boing boing article consists of the entire WIKI!
Fordite, also known as Detroit agate, is old automobile paint which has hardened sufficiently to be cut and polished. It was formed from the built up of layers of enamel paint slag on tracks and skids on which cars were hand spray-painted (a now automated process), which have been baked numerous times. In recent times the material has been recycled as eco-friendly jewelry.
This was my first thought. Paint aside, just about every material used back then to make a car had lead in it for one reason or another.
Lead based paint was more the sort used to paint houses yes? I don’t think auto paint has ever really been lead based.
I’d love the sample in the photo, that is quite beautiful.
It is also found on the cars at Cadillac Ranch in northern Texas. The roof of one of them was about 4 inches thick, by my measure.
My brother worked at the Ford assembly plant in South Chicago for 30 years. He brought one of these home for me around 1970 and I still have it, somewhere. One side was flat, somewhat polished, but the rounded side looked much like the right side in your photo for this article. This sure brought back some memories. (I also worked there 1 summer in '71 while in college. Never saw that side of the plant though.)
Some old auto paint (from the period this stuff was created) did use it, esp. in orange, red and yellow.
So if you have some Fordite, don’t lick it.
old auto paint had lots of lead, up to 20% of the formula for some shades. some auto paint still has lead in it. Probably not what is used in the us though
Minor thing: You misspelled “anthropogenic.” Also, if I wanted to be a real smartarse, I’d point out that minerals are by definition never anthropogenic. Us humans tend to be really into separating ourselves from all that icky nature stuff.
That’s a quote from the MininGeology blog, posted July 7, 2015. But the Wikipedia text looks like it was authored by “Charles Sturm” in Feb 2008, so it appears the Geology blog copied that. Was the Wikipedia text also copied from somewhere else? Who knows.
Reminds me at my old alma mater Carnegie Mellon there’s a fence that various groups and organizations paint to advertise parties, events and such. I don’t know how many hundreds of paint layers there are…
A similarly anthropogenic mineral:
Another similar stone is rainbow calsilica. Which is proooobably not a real rock as it is often advertised and is probably more like fordite.
This article maintains that calsilica is natural. Wiki doesn’t have an article, so maybe you should write it!
I feel like I failed to add a sufficient number of qualifications and I’m sorry for that. I’m not an expert on the topic, I’m just sharing a cool thing that seemed related to the cool thing up top. I have seen a lot of questions around rainbow calsilica. Particularly the image I saw of a bottlecap embedded in it. But again, not an expert. Definitely the wrong person to write an article about it.