Elemental Analysis of Stones Using Laser-Induced Breakdown Spectroscopy

We present elemental compositions of different stones found in the locality of the Mirpur region of Azad Jammu and Kashmir using laser-induced breakdown spectroscopy (LIBS). The optical emission spectra of different stones have been recorded using an neodymium-doped yttrium aluminum garnet laser (1064 nm) in conjunction with the LIBS-2000 setup to categorize the existence of various elements and studied the effects of laser irradiance on the intensities, widths, and shifts of the spectral lines. The emission spectra of Gray stones show multiple elements: Ca, Fe, Mg, Sr, Na, and Li, whereas the Half-White stones contain all these elements except Sr. It is observed that the calcium lines dominate at long wavelengths, while iron lines dominate in the shorter wavelength region. We have determined the relative strength of each element and it is found that calcium dominates in both the samples. We have also observed the effects of laser irradiance on the signal intensity and it is noted that the initial signal intensity increases with the increase in the laser irradiance, reach at maximum and then stops increasing further with the increase in energy. The electron number density has been determined from the Stark-broadened profile of the spectral lines.