A system and method are described for determining properties of particulates. The device collects particulates on the surface of an oscillating balance and compares the natural resonant frequency of the balance with the particulates with a balance without particulates. In addition, the collected particulates are illuminated with light that is absorbed by the particulates. This causes the balance to heat up, affecting the natural resonant frequency. A comparison of the natural resonant frequencies reveals optical properties of the collected particulates, which may be used to speciate the particulates.