Ok kiddo, let's talk about icosahedral twins. Imagine you have two big beach balls that are exactly the same size and shape. You can put them next to each other and they look almost the same, right? Now imagine you took one of those beach balls and cut it up into twenty little triangles.
If you lined up those little triangles in a special way, they would fit perfectly onto the other beach ball like a puzzle. This is kind of like what happens with icosahedral twins.
When some types of metals grow, they sometimes can form tiny little crystals. If two of those crystals form with the same shape but arranged slightly differently, they can fit together like those beach ball triangles. And when that happens, you get an icosahedral twin!
Icosahedral twins are really interesting because they have a special type of symmetry. Symmetry is when something looks the same no matter how you look at it. If you cut an apple in half, both halves look the same, right?
Well, icosahedral twins have symmetry that looks the same no matter how you turn it 1/5th of the way around. And that's really cool! Scientists are still learning a lot about icosahedral twins and how they form.