Use of Mineralogy and Fossils in Identifying Aggregate Sources

The state of Texas has a wide variety of rock formations from which immense volumes of crushed stone and gravel are transported annually to various types of construction projects. The development and expansion of transportation modes over the past 60 years, such as interstate highways, state and federal roadways, and intercoastal canals, have provided the means of moving industrial mineral and aggregates to construction sites across the State. Petrographic examinations indicate that quarried stone deposits and sand and gravel pits tend to have unique mineral suites and/or microfossils that can provide a "fingerprint" for each deposit. Unique indentifications of the most commonly used constructional aggregates can enable the tracing of a given aggregate material to a specific geologic source. Identifiable mineral and microfossil constituents of constructional aggregates have been used to definitively pinpoint a material's origin with a degree of certainty that has allowed the resolution of performance claims or disputes involving concrete placements. Such microscopical features have been used effectively to give expert testimony on the origins of physical evidence in civil and criminal litigation cases.