Microcrystalline and Amorphous Silica: Materials that Shaped Humanity

The use of microcrystalline silica has been documented among early hominins, with significant diversification over the last ~3 million years, from early toolmaking to applications in personal adornment and symbolic contexts. From the Oldowan onwards, both microcrystalline quartz and amorphous silica are consistently observed in the archaeological record, and they shaped aspects of human technological and behavioral evolution. This article offers insights into how mechanical, environmental, and cultural factors guided the selection of silica materials and their transformation to purposeful objects—from Pliocene hominins through to the Middle Ages. The crystal chemistry that imbues microcrystalline quartz varieties with their unique properties is reviewed, and the formation pathways for biogenic and abiogenic microcrystalline and amorphous silica are considered.