Saturday, March 28, 2009

Hexagonal Prisms in Amethyst Crystals

Amethyst is a purple form of quartz. I became fascinated with the structure of the crystals after zooming in on this photograph of an amethyst geode that I took a week ago in New Hampshire at Gemstar Gemstones in Enfield. I saw the individual crystals in the photos below. This was the first time I ever saw a hexagonal prism in "real life." I have read that the crystals have a tetrahedral structure. Tetrahedrals are one of the five Platonic Solids (regular polyhedra). I also read that amethyst crystals are trigonal, meaning they have three-fold symmetry. An excellent discussion of trigonal crystals appears here.
To see more amethyst crystals, click here.

Here, I zoomed in on the first photo. You can see the six-sided prisms here.

If you have Apple's QuickTime software click here to see an interactive QTVR crystal of amethyst. Click here to view an interactive 3D model of the amethyst structure (this will open a new browser window).

Here I zoomed in even further and clearly saw the hexagonal prism.

If only we had the time to teach polyhedra to our students in the field while we collect rocks. I know they would never forget the experience or the mathematics.

Gemstar Gemstones Set

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  1. I have a geode with amethyst crystals in it. I also have some quite large crystals of citrine -- and yes, I got them both in Brazil

  2. I adore amethyst and it is my birthstone. There is a beautiful geode in the gem shop in the city and I want it! However, it's a little expensive and I do have other priorities, which I sometimes feel like throwing out the window.

    Beautiful photos of a beautiful crystal.

  3. Beautiful photographs. Crystals should be used to teach geometry, so that people can see what a polyhedra looks like in nature.

    Have a great week.

  4. Passed by from BYBS and I can't seem to find you latest post. Ha! I'm really new in this blogging thing. I still need to learn more. And gee wish I can keep a cat in my loft. My landlord forbids it though I had cats when I was a kid.

    LOL! Would you believe that the word verif is "catio"? Cool!

  5. Those are huge pillars of amethyst, or at least it appears that way in the photos.

    It is always amazing to see such pure geometry in nature.

  6. Hi
    Amethyst crystals are hexagonal, not tetrahedral. They have six-fold rotational symmetry, while tetrahedrals crystal have 4-fold symmetry.

  7. I agree, jbacsa, as I wrote above. I read in one source that they have tetrahedral structure (they may have been talking about how the crystals are formed, I'm not sure now), but I failed to keep the source for that. I'm glad you stopped by and commented.


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