Note: The spectral mixing exercises require Flash 6.0 or higher to be installed with your browser. The free Flash player can be downloaded here.

In these Exercises the object is to determine the composition of a rock sample by comparing it to samples of known minerals. In nature, most rocks are composed of a mixture of minerals. By finding a mixture for which the combined graph matches the graph of the sample we can determine the composition of an individual rock.

In these sample exercises we'll be attempting to determine the composition of rocks on the surface of the moon. The simple exercise uses a calculated rock based on chemical analysis of samples brought back by the Apollo landings. This allows a perfect match to be made, and is intended as an introductory exercise. The advanced exercise uses real data and a much larger list of minerals. Finding a perfect match here will be quite difficult, if not impossible.

To make a mixture, select a mineral from the mineral list in the upper left. Read the description to determine if this mineral is likely to be found on the moon, and compare the sample graph to determine if it might be a component of the target. If the mineral appears likely, click the "add to mixture box" in the upper right hand corner. A box will appear in the middle section of the display bearing the mineral's name, a slider, a couple of buttons, and the percentage of the overall mixture composed of this mineral.

The proportion of a mineral in the mixture can be adjusted by moving the slider. The "X" button in the upper right corner removes a mineral from the mixture. The button just to the left of the "X" button locks the percentage of the mineral so adjusting other sliders will not cause this mineral's concentration to change.