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The Glories of Garnet Mica Schist

The views expressed are those of the author and are not necessarily those of Scientific American.


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All right, yes, I’ve been very neglectful lately, but when you see what I’ve brought back from the field for ye, you’ll forgive me. Probably. If you like garnets, certainly.

B and I returned to Icicle Gorge last weekend and did the whole loop trail. During that excursion, we found our way down to the waterside, and you would have heard exclamations like “Oh my god! They’re huge!” and “This is lousy with garnets!” – along with assorted incoherent shrieks of joy – echo from the gorge walls as I discovered boulder after boulder of schist filled with garnets, sparkling deep, rich red against the cheerful silver glitter of the mica within the stone.

Garnet mica schist, with rock hammer for scale.

Garnet mica schist, with rock hammer for scale.

You can click the photo to enlargenate. Yum!

 

People, the only thing that beats out garnet mica schist in my list of favorite rocks is blueschist. Finding a bank absolutely full of it floated my boat in a big way. Of course, I didn’t take that metaphorical boat down the stream – the rapids are killer. Not that I paid much attention to them. I had me nose to the rocks.

Getting closer to the garnet! Hammer tip for scale.

Getting closer to the garnet! Hammer tip for scale.

Back when I first fell in love with garnet mica schist, I wanted what all young lovers do: I burned with a desire to know all about it. Luckily, Elli Goeke, author of Life in Plane Light, heard my cry, and obliged with a series of posts that explain how this beautiful thing happens:

Metamorphic reactions — the basics

Mud to cordierite – sillimanite hornfels — contact metamorphism at work

Mud to garnet schist — regional metamorphism at work

There ye go. Something of substance to sink your teeth in to! I’m eternally grateful to Elli for taking the time to explain this process to a young, green, utter amateur.

Knowing how these rocks formed gives me a new appreciation for them, but I’ll admit something: my first reaction to finding them is still a fair imitation of a kid who just got an unexpected windfall for her birthday. For a time, all I can do is chase sparkles.

HUGE garnets in the Icicle Gorge schist. Hammer for scale.

HUGE garnets in the Icicle Gorge schist. Hammer for scale.

Some of the stuff I found came close to the garnet mica schist I’ve gotten from Alaska, and that one’s very, very big.

Garnet mica schist from Alaska. The garnet is roughly the size of a large pea.

Garnet mica schist from Alaska. The garnet is roughly the size of a large pea.

Unfortunately, the garnets down in Icicle Gorge have been broken and battered by the ferocious stream, and erosion isn’t doing the schist any favors, but they’re still fantastic.

Garnet mica schist, without any distractions.

Garnet mica schist, without any distractions.

You can click to embiggen any of the above photos. Set aside the proper amount of time for drooling. Reflect upon the fact that plate tectonics produces outstanding rocks like this. And if you’re ever in the Seattle area and wish to drool over these rocks in person, let me know – it can certainly be arranged!

In other news, I’ll be loading you up with some excellent posts soon, once I can extract myself from the black hole that is a tiny kitten. Between Luna and field season, it’s hard to do serious blogging – but I’ve got something special coming up. Stay tuned!

Dana Hunter About the Author: Dana Hunter is a science blogger, SF writer, and geology addict whose home away from SciAm is En Tequila Es Verdad. Follow her on Twitter: @dhunterauthor. Follow on Twitter @dhunterauthor.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. CherryBombSim 8:37 pm 07/23/2013

    Garnet mica schist was my gateway drug to geology. There were some nice ones by the creek near my house when I was in about fifth grade, and I really got into chipping out the garnets and collecting them. Then I had to learn about the different kinds and their chemistry, what angles they should be faceted, etc, etc.

    Link to this

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