THERE ARE TWO COMMONLY CONFUSED GROUPS OF MINERALS THAT MAKE UP MOST OF A GROUP OF MINERALS CALLED THE INOSILLICATES.
THEY ARE THE AMPHIBOLES AND THE PYROXENES. IN ORDER TO NARROW DOWN ON WHICH OF THOSE GROUPS THEY BELONG TO, WE HAVE TO TAKE A GOOD LOOK AT THEIR CLEAVAGE. CLEAVAGE IS THE ANGLE OR INCLINE AT WHICH A MINERAL CLEAVES OR BREAKS. THE PYROXENES HAVE AN ANGLE OF CLEAVAGE AT TWO 90* ANGLES WHILE THE AMPHIBOLES HAVE AN ANGLE OF CLEAVAGE AT 56* AND 124* ANGLES.