Abstract: Viséite is a poorly crystalline mineral which is difficult to study by X-ray diffraction pattern. NMR is a very useful technique to study such poorly crystalline minerals, and ³¹P, ²⁷Al, and ²⁹Si MAS NMR in conjunction with powder XRD results show that at least our visrite sample is not a single phase with a structure analogous to that of analcime as previously reported. Rather, it is very disordered with a structure similar to that of crandallite and includes other phases including an undefined aluminophosphate, opal, and a framework aluminosilicate, probably a zeolite. The previously reported variations in the Si content of visrite are probably due to variable amounts of opal and the framework aluminosilicate.