ABSTRACT: Laser-induced breakdown spectroscopy (LIBS) is a rapid, low-cost analytical method with potential applications in quantitative analysis of soils for major and trace elements. Here we examined the effects of matrix and target particle sizes on measurements of soil composition by LIBS. The experimental approach involved milling a clean sand matrix to six different particle sizes (medians: 19 to 810 µm) and spiking each with two different iron (Fe) minerals (medians: 1 and 74 µm) to a constant concentration of 5 wt%.