Ca0-SiO2-MgO Diagram. This three-component diagram is designed to help you check your understanding of plotting coordinates for a ternary (3-component) composition diagram. Click on the diagram at the composition requested. A red dot should appear where you clicked. If that dot matches the requested composition, a blue circle centered on the requested composition will appear behind your dot. If your click is not on the requested composition, press the try again button and repeat the test. Return to Text