pyrrhotite
noun
pyr·rho·tite ˈpir-ə-ˌtīt 
: a bronze-colored mineral of metallic luster that consists of ferrous sulfide and is attracted by a magnet
Example Sentences
Recent Examples on the Web Concrete used in homes in Eastern Connecticut contained the mineral pyrrhotite, which degraded foundations. 
Jesse Leavenworth, courant.com, 8 June 2021 Fresh funding for the study of crumbling foundations in the state, appears to be paying dividends, lowering the cost of testing for pyrrhotite to nothing for some homeowners, including residents at Ryefield Condominiums in Vernon. Steven Goode, courant.com, 26 Oct. 2020 This pyrrhotite problem is the first of its kind in the United States. Washington Post, 29 July 2019 The Hartford Courant reports tens of thousands of homes could be at risk of having a foundation fail because of an iron sulfide called pyrrhotite. USA TODAY, 12 Nov. 2019 The material containing pyrrhotite has been traced to a Willington quarry used between 1983 and 2015 by a now-defunct concrete company. Washington Post, 29 July 2019 Many of those homes require repairs because a chemical known as pyrrhotite was used in the concrete when the homes were constructed, chiefly in eastern Connecticut. Christopher Keating, courant.com, 6 June 2019 According to a state report, a mineral known as pyrrhotite — used in the concrete aggregate for the foundations that are now crumbling — is partly to blame. Kathleen Mcwilliams, courant.com, 4 June 2018 The issue was traced to a quarry in Willington and a mineral — pyrrhotite — that causes the concrete to deteriorate. Russell Blair, courant.com, 10 May 2018 See More
Jesse Leavenworth, courant.com, 8 June 2021 Fresh funding for the study of crumbling foundations in the state, appears to be paying dividends, lowering the cost of testing for pyrrhotite to nothing for some homeowners, including residents at Ryefield Condominiums in Vernon. Steven Goode, courant.com, 26 Oct. 2020 This pyrrhotite problem is the first of its kind in the United States. Washington Post, 29 July 2019 The Hartford Courant reports tens of thousands of homes could be at risk of having a foundation fail because of an iron sulfide called pyrrhotite. USA TODAY, 12 Nov. 2019 The material containing pyrrhotite has been traced to a Willington quarry used between 1983 and 2015 by a now-defunct concrete company. Washington Post, 29 July 2019 Many of those homes require repairs because a chemical known as pyrrhotite was used in the concrete when the homes were constructed, chiefly in eastern Connecticut. Christopher Keating, courant.com, 6 June 2019 According to a state report, a mineral known as pyrrhotite — used in the concrete aggregate for the foundations that are now crumbling — is partly to blame. Kathleen Mcwilliams, courant.com, 4 June 2018 The issue was traced to a quarry in Willington and a mineral — pyrrhotite — that causes the concrete to deteriorate. Russell Blair, courant.com, 10 May 2018 See More Word History
Etymology
modification of German Pyrrhotin, from Greek pyrrhotēs redness, from pyrrhos red, from pyr fire — more at fire
First Known Use
1868, in the meaning defined above