All other isotopes of aluminium are radioactive. Quite possibly the most secure of such is 26Al, that has a 50 percent-life of 717,000 many years: whilst it was existing coupled with secure 27Al from the interstellar medium from which the Solar System fashioned (believe that to are made by stellar nucleosynthesis https://aluminiumgreenhouse02233.myparisblog.com/38157263/the-definitive-guide-to-aluminium-greenhouse