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