This article discusses different varieties of quartz that are used as gemstones. A general description of each is given, including its historical background and physical makeup. This page is part of an excellent, detailed website about...

Hillman Hall of Minerals and Gems offers an opportunity to explore a variety of ores, metals, gems, and other specimens displayed at the Carnegie Museum of Natural History. This resource offers an excellent collection of photos for...

This resource provides photographs of and information about various minerals.

Wikipedia provides this encyclopedia entry for cement that features its history, production, and use as a building material, as well as links to related topics.