A rapid, simple and accurate procedure for direct derivative spectrophotometric determination of beryllium in some geological samples is described. Derivatization of spectra is a straightforward technique for enhancing selectivity. This process helps to overcome spectral interference and thus results in an increase in test selectivity. The process of derivatisation is a widely recognized technique for separating usable signals from noisy data. Through the application of first, second, third, and fourth derivatives, it has been determined that the selectivity is enhanced by the employment of the first derivative. The method is based on the reaction of beryllium II with rhodamine B in the presence of sodium hydroxide to form a stable purple complex, which has an intense absorption at 524 nm in zero order and 504 nm in 1st. order derivative spectrophotometry. The complex was examined by FTIR spectroscopy and ESEM-EDX. The average molar absorptivity (ε) and Sandell's sensitivity of the complex were found to be 0.22×103 M−1 cm−1 and 4.09×10-2 respectively. Beer's law was obeyed over the range of 0.5 – 10 ppm. Removing interference from beryllium measurements caused by common cations is as simple as precipitating by ammonia at pH 9 and utilising the 1st order derivative. Successful determination of beryllium II in various geological materials has been achieved using this approach.