Most aluminum sold worldwide is in fact an alloy of 92-99% aluminum with the rest being other elements such as magnesium, iron or zinc. The various recipes are tailored for the specific use with each of these elements offsetting a shortcoming of pure aluminum while adding some desirable quality such as extra strength or resistance to corrosion. Even “pure” aluminum as commercially available, the so-called aluminum 1100 series, is really only around 99% pure as higher levels of purity require expensive extra processing that doesn’t end up being any better or worse.

But 99.99% pure aluminum is a lab concoction useful only in very specialized applications.

Like a miniature disco ball seemingly hovering without support, here we have a sphere of this ultra-pure aluminum. These spheres were engineered as specialty bearings which need to be lightweight and (for whatever reason) free of impurities. Far more expensive and delicate than their steel counterparts their relatively high cost is due to their needing to be individually machined.