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Rocks Turn Paperclip Invisible??

Ugh. Monday. But to brighten up your otherwise dreary beginning of the week, here’s a brand new Mineral Monday!

Calcite Crystals photo from Flickr by Orbital Joe

Calcite is our Mineral this week. It’s a carbonate mineral, which means it has the carbonate ion CO3^(2-). Calcite is fun in general, because being a carbonate mineral means that it’s mildly reactive. Dropping a weak acid on a calcite sample causes it to bubble- just like vinegar and baking soda (coincidentally, another carbonate).

It has beautiful trigonal-rhombohedral crystal structure and is usually clear or milky white.

But calcite is also in possession of some great optical properties, that have recently caused an uproar in the physics world- or at least in the headlines about the physics world.

Headlines last week started screaming about Invisibility Cloaks. Star Trek and Harry Potter were both invoked, as blogs and magazines reported a study by scientists at the University of Birmingham and MIT where researchers has used calcite crystals to render a paperclip invisible. Yes. A paperclip.

Paperclip Photo from Flickr by Kylemac

Most invisibility research has focused on using highly engineered materials to make microscopic things disappear. Which is cool research, but kind of pointless right now, as they’re…microscopic. But these scientists have figured out that calcite’s unique crystal structure  (which makes text float off the page or double when a calcite crystal is placed over it) can actually create a kind of ‘invisibility cloak’ for objects as massive as paperclips. The scientists essentially glued together two calcite crystals so that the optical properties of one were placed in perfect opposition to the other’s- this made any object placed behind the two attached crystals appear to not be there: hence, the Curious Incident of the Invisible Paperclip.

A demonstration of the optical properties of Calcite Photo from Flickr by Orbital Joe

Of course, before all the Star Trek and Harry Potter fans out there start celebrating, there are a few issues. The primary one being that calcite is visible. It might seem clear a lot of the time, but just like you can see glass or clear plastic, you can see it. Also, it works right now just as a shield- not a 3-D cloak, making movement of anything difficult.

Sadly, the guys that wrote the study provided no awesome videos or pictures, or even non-awesome videos and pictures, which is just depressing. To All Scientists: If you’re going to invent invisibility cloaks, and announce said invention to the world, please be prepared for a public demonstration. We’ve read enough fiction to want to see such things for ourselves.

For a good description of Calcite’s optical properties click here

3 Comments

  1. Matt Hall wrote:

    Nice post. Calcite was actually in the news twice last week, as the testing of a long-standing theory about Viking navigation was reported on. It was picked up by various news organizations, but I read it at New Scientist here: http://bit.ly/h3jT0U. you didn’t mention that the two images you see through calcite have mutually orthogonal polarization (there has to be a simpler way to write that!), and apparently it’s possible the Vikings exploited this to locate the sun in foggy and cloudy conditions. Very cool!

    Monday, February 7, 2011 at 8:16 pm | Permalink
  2. MBGriggs wrote:

    Matt- thanks so much for your comment and that link! I totally missed that- it’s a fantastic study. Now that they’ve proved it’s possible with instruments, I’m really looking forward to seeing if they can use it to navigate using just calcite. It would be an amazing feat of experimental archaeology if they make it happen. And as for mutually orthagonal polarization- I was having a hard time figuring out how to say that simply, but you’re right, it’s important. Definitely something to work on!

    Monday, February 7, 2011 at 8:49 pm | Permalink
  3. LMG wrote:

    Very interesting post–definitely a Monday-brightener!

    Tuesday, February 8, 2011 at 9:38 am | Permalink

5 Trackbacks/Pingbacks

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  2. [...] is split and follows two parallel paths through it, which explains how calcite makes objects look doubled. The relative brightness of the two images—the amount of light following the two different [...]

  3. [...] is separate and follows dual together paths by it, that explains how calcite creates objects look doubled. The relations liughtness of a dual images—the volume of light following a dual opposite [...]

  4. [...] is split and follows two parallel paths through it, which explains how calcite makes objects look doubled. The relative brightness of the two images—the amount of light following the two different [...]

  5. [...] is split and follows two parallel paths through it, which explainshow calcite makes objects look doubled. The relative brightnessof the two images—the amount of light following the two different [...]

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