Symmetry in crystal structures- please help!!! Hi there, I was hoping someone here could help explain a few things about crystal symmetry to me cos it hs me so confused (we've been doing crystals for 2 weeks and things up til now have been ok, I'm just getting myself muddled as usual!). The attachment is of the diagram handed out with our assignment this week and for one of the questions we've to spot mirror planes, glies planes, screw axes and centres of symmetry. All I've come up with so far has been 2 mirror planes marked in red, 2 screw diads marked in red splodges, 2 diagonal glide planes marked in green (with translation in the plane of the paper) and a centre of symmetry marked in purple. There are supposed to be more mirror planes - can anyone hint to me where they should be? I think there's supposed to be on in the plane of the page but I've no idea where to find it. Can anyone giveme a hint? Btw, I've checked up online that it should be orthorhombic, but a friend of mine at uni thinks it's tetragonal because we can't find enough mirror planes. If anyone is good at recognizing these things you'd make me a very happy girl. :tongue2: If anyone could give me a hand at all with this or let me know where I'm going wrong etc, I'd be really grateful. At the moment all I seem to be doing is reading about crystals and actually having someone to sort out a few of the bits and pieces I'm stuck on would be fantastic. Thanks. Claire Btw, sorry for posting this in here, I was just hoping more ppl might see it!