A method of spectroscopic analysis of a yellow diamond gemstone for determining whether the diamond has been artificially treated to change its colour, the method comprising: - generating light emission from a diamond upon optical excitation at an excitation wavelength from 600 nm to 675 nm, wherein the diamond is exposed to a light beam that generates optically excited emission and scattered light at room temperature; - optically producing a dispersed light emission; - detecting the dispersed light emission across a collected spectral region by means of a photodetector device to electrically generate output signals, wherein the collected spectral region comprises emission wavelengths of from 670 nm to 750 nm; - processing the output signals to produce a spectral intensity distribution as a function of emission wavelengths, characterised in that the method further comprises: - analysing the spectral intensity distribution to determine the presence or absence of a spectral pattern comprising either an intensity peak at 681 nm or a combination of intensity peaks at respective wavelengths 705 nm and 725 nm, wherein the spectral pattern is at least one spectral feature selected from the group consisting of an intensity peak at 681 nm, two intensity peaks positioned at the respective wavelengths of 705 nm and at 725 nm, and three intensity peaks positioned at respective wavelengths of 681 nm, 705 nm and 725 nm; - if, as a result of analysing, a spectral pattern is determined to be present, establishing that the diamond has been artificially treated to change its colour, and - if, as a result of analysing, a spectral pattern is determined to be absent, establishing that the diamond has not been treated to change its colour. - generating light emission from a diamond upon optical excitation at an excitation wavelength from 600 nm to 675 nm, wherein the diamond is exposed to a light beam that generates optically excited emission and scattered light at room temperature; - optically producing a dispersed light emission; - detecting the dispersed light emission across a collected spectral region by means of a photodetector device to electrically generate output signals, wherein the collected spectral region comprises emission wavelengths of from 670 nm to 750 nm; - processing the output signals to produce a spectral intensity distribution as a function of emission wavelengths, characterised in that the method further comprises: - analysing the spectral intensity distribution to determine the presence or absence of a spectral pattern comprising either an intensity peak at 681 nm or a combination of intensity peaks at respective wavelengths 705 nm and 725 nm, wherein the spectral pattern is at least one spectral feature selected from the group consisting of an intensity peak at 681 nm, two intensity peaks positioned at the respective wavelengths of 705 nm and at 725 nm, and three intensity peaks positioned at respective wavelengths of 681 nm, 705 nm and 725 nm; - if, as a result of analysing, a spectral pattern is determined to be present, establishing that the diamond has been artificially treated to change its colour, and - if, as a result of analysing, a spectral pattern is determined to be absent, establishing that the diamond has not been treated to change its colour. <EOS>