Considerable amount of uranium and thorium are found in our local zircon and the level is much higher than the maximum value adopted by Malaysia and many importing countries. Energy Dispersive X-ray Flourescence (EDXRF) proves to be a very valuable tool in the determination of these radioactive elements as it can perform the analysis simultaneously in shorter time. Quantitative analysis of this mineral involves the use of a fundamental parameter technique developed by National Bureau of Standard, USA and Geological Survey Canada (NBS-GSC FPT). The analysis for tin slag is more challenging as there is no reference standard of similar material. Thus the standard addition method was applied to correct the error from the matrix of the sample.