| Well, I was a geology major as an undergrad (25 years ago) so I will take a stab. these fractures are just the natural way this granite wants to break....or cleave. Granite varies widely in its chemical/mineral composition and that will effect the cleavage planes (or lack thereof in this case). These look like conchoidal fractures (somewhat rounded, not parallel like you see in micas for instance). You see this in rocks with high quarts/silica content. Think of obsidian/volcanic glass (which is almost pure silica) and how it fractures....extremely conchoidal. It reflects the underlying matirx/structure of the atoms/elements of the rock. Hope that is clearer than mud. Claire |
Here is a link that might be useful: mineral fractures
