Can someone please name some rocks with cleavage? (no bad puns please)

If a rock that has lines of cleavage were cut and polished into a sphere and then broken, would it still break along those lines?

Some rocks with cleavage are: Slate, phyllite, schist, and gneiss. I think that if cut and polished into a sphere they would still tend to split along the lines of cleavage. You might find the following site helpful:Click This

Plagioclase is an interesting rock with cleavage, because it breaks at almost a 90 degree angle. It's an attractive looking rock, white, sort of like quartz. Yes, when struck, a rock will break along its natural cleavage lines, even if it has been shaped previously by cutting.

Only minerals have true cleavage which is a characteristic directly related to their atomic structure. Some metamorphic rocks have foliated textures and in the case of slate this so closely emulates cleavage that it is called slaty (or rock) cleavage.

Plagioclase is not a rock it is a sub-group of the Feldspar Group of minerals. The feldspars have two planes of cleavage that intersect at nearly right angles (90 degrees).

Other minerals with cleavage:

• Flourite
• Halite
• Calcite
• Biotite

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