Brown Bag Lecture: The Recognition of Pseudomorphism: Mineral Chemistry as a Historical Science

Lunchtime Lectures
Monday, May 14, 2018
12:00 p.m.–1:00 p.m.
Science History Institute
315 Chestnut Street
Philadelphia, PA 19106
United States

Join us for a Brown Bag Lecture by Stephen Irish, Presidential Visiting Fellow at the Science History Institute.

A pseudomorph is a mineral with the outward form proper to a different mineral, whose place it has taken as a result of some chemical process. This talk surveys the history of the acceptance of pseudomorphism, which appears to have been little studied. Mineralogists began to take notice of pseudomorphs in the second half of the 18th century, but it was not until the mid-19th century that the phenomenon was fully recognized by scientists. At least two factors impeded its acceptance. First, it was unclear whether pseudomorphism could be made physically intelligible within the crystallographic theories that predominated in this period. Second, the phenomenon was inconvenient for the central goal of mineralogy in the years around 1800: to provide a detailed description and taxonomy of a stable natural order. As the century progressed, crystallographers came to accept pseudomorphism, even where they could not fully explain it. Mineralogists perceived the great positive potential of pseudomorphs to offer insight into the historical processes of mineral formation extending into the deep past.

About the Speaker

Stephen Irish completed a PhD in history and philosophy of science at the University of Cambridge in 2016. He works primarily as a historian, with an interest in 18th- and 19th- century chemistry and mineralogy. His thesis studied the introduction of crystallographic theories into British scientific practice in the first two decades of the 19th century. In 2017 he was awarded the Partington Prize by the Society for the History of Alchemy and Chemistry for his article “The Corundum Stone and Crystallographic Chemistry.” He is currently doing research at the Science History Institute as a short-term Presidential Visiting Fellow.

About the Series

Brown Bag Lectures (BBLs) are a series of (mostly) weekly, informal talks on the history of chemistry or related subjects, including the history and social studies of science, technology, and medicine. Based on original research (sometimes still in progress), these talks are given by local scholars for an audience of the Institute staff and fellows and interested members of the public.