Hedgehog rock

When I look at a rock sample I do it as a geologist. I try to identify the constituent minerals which would allow me to name it. But people are different. Their experience and interests vary. When my children saw the photo below of a rock sample I brought from Finland they immediately knew that it resembles a hedgehog:


This is very old (from the Archaean) and compositionally fascinating igneous rock known as carbonatite. It is mined as a source of phosphate (green mineral is fluor-apatite) but for some this is a hedgehog-rock. Do you see it?

Dark patch (mineral phlogopite) is the eye and another slightly curved piece of phlogopite above it is an eyebrow. The pointy left edge of the rock is a nose.

That alone is not enough for me to write a silly interlude between more serious posts about rock types and minerals but there is one more interesting aspect. This carbonatite comes from the Siilinjärvi mine. The name has meaning for me because in my native Estonian the placename would be spelled Siilijärve. The similarity is strong because Estonian and Finnish as related languages have numerous similar words. But what about that? Well, in English the place name would be Hedgehog’s Lake (siili means hedgehog and järvi is lake). So the rock sample that strongly and absolutely accidentally resembles hedgehog actually comes from a deposit that is also somehow associated with this animal.

I will very soon write about carbonatites in a more serious manner. Stay tuned!

By the way, the rock sample is 19 cm in width. White mineral is calcite. The rock itself is plutonic calcite-carbonatite (sövite).

1 comment to Hedgehog rock

  • Dr. K.N.RAO

    Sir, where can I get optical properties of rare and uncommon minerals like burbankite, carbocerite, spurrite, merwinite, carnegiete, larnite, Betafite, BRITHOLITE and host of REE minerals found in carbonatites. If not possible to provide these properties right now, I suggest (request) that you may kindly include the optical properties in your forthcoming publication about carbonatites. Thanking you, K.N.RAO. knraogeol@yahoo.co.uk.