Laser-induced breakdown spectroscopy (LIBS) was used to yield quantitative elemental information of ore samples. A Nd∶YAG laser beam with wavelength of 1064 nm was focused on the sample surface to generate laser plasma. The plasma atomic emission spectra were recorded by a micro-spectrometer. In order to optimize experimental condition, dependence of the spectral line intensity upon laser pulse energy and time delay of signal collection with respect to the initiating laser pulse were investigated. Strong influence of the laser pulse energy on the spectral signal was found in the experiments. However, time-delay had less effect on the spectra within the range of the selected time delays. Spectral lines of silicon (Si I line at 251.6 nm) and magnesium (Mg I line at 285.2 nm) were separately used to determine, the silicon and magnesium contents in the samples based on the external standard method. The relative standard deviations (RSDs) of the measured elemental contents relative to those standard values were 7% and 3% respectively for the silicon and magnesium elements. It provides a basis for the feasibility of rapid detection and elementary analysis with the laser-induced breakdown spectroscopic technique.