Petrography lower if wholly or partly vitreous. The specific gravity of the more common rocks range from about 2.5 to 3.2. Archaeologists use petrography to identify mineral components in pottery. This information ties the artifacts to geological areas where the raw materials for the pottery were obtained. In addition to clay, potters often used rock fragments, usually called "temper" or "aplastics", to modify the clay's properties. The geological information obtained from the pottery components provides insight into how potters selected and used local and non-local resources. Archaeologists are able to determine whether pottery found in a particular location was locally produced
Nature study students, who were influenced by this philosophy, went on to provide the nature study knowledge in public schools. It was Agassiz who coined the phrase, "Study nature, not books." Nature study can be described as "conceiving of the movement as a loose coalition of communities composed of individuals, societies, and institutions able to find some common ground in the study and appreciation of the natural world". In "Leaflet I: What Is Nature-Study?" from a 1904 collection nature study lessons, Liberty Hyde Bailey presented the following description of nature study: NATURE-STUDY, as a process, is seeing the things that one looks