Pegmatites and Bubblegum

Yeah. I said it.

Pegmatites.

PEGMATITES.

OK, now I can breathe. Seriously, it’s no big deal.

This is a geology post.

Pegmatites are just perfectly ordinary igneous rocks (those that crystallize from the cooling of molten rock) that have really, really, really big crystals in them. That’s all.

With igneous rocks, big crystals means that cooling took place over a really, really, really long time.

Take granite, for example.

Granite. Quartz (grey) and feldspar (orangy-pink) are easy to see. Credit: Mark Wilson, WikiMedia Commons

This is a rock that is commonly incorporated into table tops. Granite is composed mostly of the minerals quartz, orthoclase feldspar (or K-feldspar), sodic plagioclase feldspar, and muscovite mica. And, as in the photo above, the crystals are visible to the naked eye but still generally smaller than the tip of a person’s finger.

For an igneous rock to be called a pegmatite, the crystals need to be one centimeter in diameter or larger. In other words, the crystals need to be bigger than a finger tip. Many times, the crystals are much, much larger.

Like feet across. Huge. Massive. Giant.

Like so big, you could make an entire gravestone out of one single quartz crystal from a granitic pegmatite.

Have you seen this?

AKA ‘Bubblegum Rock.’ Photo by Van King.

Read more about the history of this monument here.

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About Penny

Scientist (Paleontology, Geochemistry, Geology); Writer (Speculative and Science Fiction, plus technical and non-technical Science); Mom to great boy on the Autism spectrum; possessor of too many hobbies.

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