Microanalysis of Hafnian Zircon

As revealed by FE-SEM and electron probe microanalysis, we report that hafnian zircon (Zr,Hf)SiO_4 with Hf/Zr atomic ratio up to 1.0 is present in the famous Stewart pegmatite, Pala District, San Diego County, California. The Stewart mine, as part of the gem-bearing and rare element- bearing granitic pegmatites in Southern California, has been mined for pink tourmaline and purple lepidolite for over a century. Zircon is known to be one of the most important minerals for dating rocks and studying trace element geochemistry. Hafnian zircon and hafnon (HfSiO_4) are rare in nature. This investigation is to understand the occurrence, composition and genesis of hafnian zircon, which may insight as to how the Stewart pegmatite and various pink tourmalines formed.