FMF - Friends of Minerals Forum, discussion and message board

[marco campos-venuti]

It's a stupid question or a fundamental topic?

[Josele]

Since quartz prisms are always twinned in any case would be a twin of twins!

But I think not, parallel growth crystals are not twins because they share the same crystal lattice, there is not a boundary between them and not necessarily the geometrical "contact plane" is a symmetry plane of the set.

Can see twinning definition here: https://www.crystallography.fr/mathcryst/twins.htm

[marco campos-venuti]

Ok, it was a stupid question!

[Mark Ost]

I don't think the question was stupid. God knows all the rules are impossible to remember and as you know twin laws are not always obvious.