The Internet is, predictably, abuzz with rumors about the iPhone 5, which is most likely due out in October. But by far the more interesting rumor that blogs are circulating is that Apple’s new smartphone is going to be made out of “metallic glass.”

Leading many to ask: what the heck is that?

First off, it isn’t glass, or at least, it isn’t like any normal kind of glass. It isn’t transparent, and so it won’t be used for the iPhone’s screen. It’s also stronger and resistant to bending, denting, shattering and scratching, according to the Los Angeles Times. The big difference between metallic glass and metals as we usually encounter them is in the crystalline structure, or lack thereof. Here’s an explanation from Science Daily way back in 1998:

To scientists, a glass is any material that can be cooled from a liquid to a solid without crystallizing. Most metals do crystallize as they cool, arranging their atoms into a highly regular spatial pattern called a lattice. But if crystallization does not occur, and the atoms settle into a nearly random arrangement, the final form is a metallic glass.

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