The term used to describe the shape of a mineral that has three directions of cleavage intersecting at 90 degrees is cubic.

Here's why:

* Cleavage: This refers to the tendency of a mineral to break along specific planes of weakness.

* Cubic Cleavage: When a mineral has three directions of cleavage that intersect at 90 degrees, it forms a cubic shape. This means the mineral will break into smaller cubes.

Examples of minerals with cubic cleavage:

* Halite (rock salt): Known for its perfect cubic cleavage.

* Galena: Also exhibits cubic cleavage, though it can be less perfect than halite.

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