A semi-quantitative analysis of heterogeneous particles originating from the surface of environmentally exposed green tuff specimens has been carried out using the detection-frequency technique in laser microprobe mass spectrometry (LAMMS). In the detection-frequency technique the peak abundance ratio is used as an index in multiple mass-spectrometry measurements. This technique is considered to be useful for semi-quantitative analysis of heterogeneous samples, such as particles and aerosols adsorbed on a surface. Since the detection frequency of sulfur oxides obtained from stone specimens exposed to various environmental conditions correlates well with the sulfur amounts measured by EDX analysis, we suggest that the detection-frequency technique is appropriate for application to the semi-quantitative analysis of heterogeneous samples by LAMMS. Moreover it has revealed possible to estimate the concentration of acidic components (sulfur oxides and nitrogen oxides) at the surface of green tuff specimens for environmental monitoring.