Autofluorescent chalcedony in human brains from elderly patients

Chalcedony, a microcrystalline form of silica (SiO(2)), has been found in the human brains of elderly patients by using a standard optical petrographic microscope. We document here our visualization of chalcedony using a Leica TCS - SP2 confocal laser scanning microscope. Sections of human brain were collected after autopsy from elderly patients. The autofluorescent character of chalcedony allowed us to obtain three-dimensional images of the crystals and mature prismatic quartz (chalcedony) was observed. Chalcedony occurred as rhombohedral (trigonal) crystals approximately 30 microm in size distributed in patches or aggregates. A less mature silica polymorph of about 1- 2 microm in size was detected near the crystals. This is the first time that biogenically-produced crystalline mineral as autofluorescent crystal aggregates has been observed in the human central nervous system of elderly patients using confocal laser scanning microscopy.