The first line in the Wikipedia article for "Glass" reads:

Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics.

Emphasis, mine.

From what I've been taught at school, if a solid is amorphous then it is necessarily non-crystalline and vice versa. (Of course, you could convert a given sample of an amorphous solid to some crystalline form...but it would no longer be amorphous now would it?).

The "non-crystalline amorphous" pleonasm adopted by Wikipedia seems to suggest the existence of (yes, I know this sounds stupid) crystalline amorphous solids.

Can something (I'm using glass as an example) be both "crystalline" and "amorphous?"

If not (as I suspect is the case), then why does Wikipedia use the pleonasm "non-crystalline amorphous" when describing glass? Is it purely for emphasis?

Yes, I've already seen this question here, and no, my question's not a dupe of that.

Sure, it's possible to convert an amorphous solid to a crystalline solid (proper melting and cooling should do it), I'm not questioning that.

What I am questioning, is whether a crystalline amorphous solid can exist. For example, glass has both (non-crystalline) amorphous and crystalline (non-amorphous) phases.... but does it have crystalline amorphous phases? Yes? No? Why?


closed as off-topic by Mithoron, Nilay Ghosh, Todd Minehardt, Curt F., Jannis Andreska Aug 25 '17 at 17:42

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    $\begingroup$ Here is an amorphous crystal en.m.wikipedia.org/wiki/Crystal (look in the first images) $\endgroup$ – santimirandarp Aug 25 '17 at 9:27
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    $\begingroup$ Possible duplicate of Does crystalline glass exist? $\endgroup$ – A---B Aug 25 '17 at 9:31
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    $\begingroup$ Maybe you can say " amorphous crystal" because it has some periodic arrangements but they are lost in the distance. You can find this on Wikipedia also: amorphous (from the Greek a, without, morphé, shape, form) or non-crystalline solid is a solid that lacks the long-range order that is characteristic of a crystal. $\endgroup$ – santimirandarp Aug 25 '17 at 9:32
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    $\begingroup$ This seems to be a question on English usage more then Chemistry. I prefer the Wikipedia phrase since it emphasizes the difference. $\endgroup$ – Jon Custer Aug 25 '17 at 11:24
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    $\begingroup$ I'm voting to close this question as off-topic because it's about semantics $\endgroup$ – Mithoron Aug 25 '17 at 11:31