What is this mineral wool?

She— What is this mineral wool one reads so much about?
He— Mineral wool? Why, that's the wool they shear from hydraulic rams.
From The New York Times (Sunday Magazine 7 Mar 1897), 16.
See also:
- Mineral Wool or Mineral Cotton - article from Appleton's Annual Cyclopaedia for 1891
- Mineral Wool From Limestone - article from Stone Magazine (1898)
- Today in Science History event description for the opening of Crystal Chemical Works rock wool factory on 1 Jun 1897.
- Mineral Wool - article from Iron Age as reprinted in Scientific American(1878)