Final answer:
The mineral described with three planes of cleavage and breaking into rhombs is most likely calcite, which matches the described cleavage characteristics.
Step-by-step explanation:
To determine the identity of a mineral with three planes of cleavage where one plane is inclined and which breaks into rhombs, we must consider the cleavage characteristics of the provided minerals. Only one mineral listed fits these criteria: calcite. Calcite is known to cleave in three directions not at right angles and typically forms rhombohedral cleavage fragments. In contrast, mica cleaves in one direction (sheets), amphibole has two distinct cleavage angles at 60 and 120 degrees, pyroxene displays two cleavages at approximately 90 degrees, and halite cleaves into cubes. Therefore, the described mineral in the question is most likely calcite.