There's one type of crystal that's been at the forefront of everyone's mind over recent weeks - at least in the UK. I am, of course, talking about the glorious hexdendritic dihydrogen monoxide. Crystals are normally things you have to go out looking for to find, but not at the moment. You could hardly avoid them, whizzing over your head in powdery ballistic spheroids, or joining forces in a bold attempt to stop the trains going anywhere.
Of course, I'm talking about that delightful thing called snow. When you see satellite photographs showing the entire country covered by a white blanket, you get a sense of the scale of it. Crystals, crystals, everywhere...
So does ice count as a mineral? It seems like a tricky one, at first. According to the International Mineralogical Association's official definition, a mineral is a solid, chemically homogeneous and normally crystalline substance that formed geologically. Well, ice is certainly solid (when it's not melted, of course), and it's certainly a homogeneous crystal... in fact, ice does fit all the criteria.
It turns out that ice is indeed defined as a mineral by the IMA. It could hardly not be, really. If it melted at a couple of hundred degrees, instead of zero, then you'd never think to question it (it wouldn't rain either, of course, and there wouldn't be any oceans, tea, or indeed living things; so you'd probably have better things to not worry about). Where was I? Oh yes: ice. It even forms familiar types of crystal growth... here are some stalactites, for example:
Ok, so snowflakes are a bit weird, though. It's said that every snowflake is unique, and it's probably true... but the shape still follows simple rules. Like apatite, beryl and wurtzite (I like that one!), ice has hexagonal crystal symmetry. It tends to grow more quickly at the tips of the hexagon, though. Each spine often branches repeatedly, leading to the typical snowflake shape: