Rock-crystal quartz

At the coastal sites, graywacke and quartzite cobbles were used extensively in the production of large crude chopping tools, whereas the finegrained materials, including rock crystal quartz, were used to produce microlithic assemblages. These small tools are generally assumed to have been hafted as barbs or projectile points. 

At the inland site of Fiais, the absence of a local source of river or beach cobbles probably accounts for the limited importance of quartzite and gray-wacke at the site. Large cobble chopping tools made of these materials are absent from the site. Flaked rock crystal quartz is common at Fiais, a fact suggesting that these crystals may occur naturally in the area (6). 

---