An optical probe for use in infrared, near infrared, Raman, and other spectrometers includes a probe outer surface with a cavity defined therein. The probe emits light into a sample via emission locations on the probe outer surface, at least one being in the cavity. The light emitted into the sample is then collected at collection locations which include at least two of (a) a reflectance collection location situated on the probe outer surface for collecting diffusely reflected light from any adjacent sample; (b) a transmittance collection location situated in the cavity and receiving light transmitted across the cavity from an emission location situated on an opposite side of the cavity; and (c) a transflectance collection location situated in the cavity and receiving transflected light emitted from an emission location in the cavity, with such light being reflected from a side of the cavity opposite the transflectance collection location.