Over the past twenty years our understanding of the Middle Preclassic (900–300 BCE) period has become much clearer through archaeological investigations at a number of sites located in the Upper Belize River Valley region of the eastern Maya Lowlands. While the picture of Middle Preclassic Maya life, including their material culture, has sharpened, there are aspects that remain uninvestigated. One artifact type, identified as greenstone triangulates, has been found at several Belize Valley sites and in a variety of contexts. Although a number of these multifaceted, polished groundstone items have been recovered, little research has focused on their distribution and function in the archaeological record. An evaluation of these items from primary contexts provides data for determining how they were used in daily social and/or ritual activities throughout the lowlands. Comparative data from other regions of Mesoamerica are also discussed. A detailed geological and petrographic pilot study of a sample of greenstone triangulates is provided, pointing conclusively to early, long-distance and complex exchange networks in exotic raw materials.