Bern-4M muscovite from Switzerland was investigated via X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and thermoluminescence (TL). Muscovite has the theoretical formula KAl2 (AlSi3O10)(FOH)(2), or (KF)(2)(Al2O3)(3)(SiO2)(6)(H2O). Chemical analysis of the muscovite sample was carried out using EDS for major oxides. The results indicate that muscovite includes oxygen (59.1%), silicon (18.86%), and aluminum (15.22%) as major elements and contains low concentrations of potassium, magnesium, and sodium. In standard muscovites potassium use to be 10% and oxygen 47%, probably the sample was strongly lixiviated before the analysis. The thermoluminescence spectrum exhibits a wide glow peak located at 250 degrees C with a shoulder peak at high temperature region. Trap depth and frequency factor were calculated using Hoogenstraaten's method and found to be 1.16 eV and 1.4 x 10(10) s(-1), respectively. Reproducibility test indicated that the values within +/- 5% were obtained after 15 cycles. The storage time experiments were performed for different time periods up to 1 week for dark fading.