Mineral wool (English Wikipedia)

Weiner, Ethan. Acoustic Treatment and Design for Recording Studios and Listening Rooms. "Without question, the most effective absorber for midrange and high frequencies is rigid fiberglass."https://www.ethanwiner.com/acoustics.html#rigid%20fiberglass.

europa.eu

"Man-made mineral fibre (MMMF) is a generic name used to describe an inorganic fibrous material manufactured primarily from glass, rock, minerals, slag and processed inorganic. The MMMF produced are non-crystalline (glassy, vitreous, amorphous)." [1] Recommendation from the Scientific Committee on Occupational Exposure Limits for man made-mineral fibres (MMMF) with no indication for carcinogenicity and not specified elsewhere

Spon, Ernest. Workshop Receipts ... London: E. & F. N. Spon, 18831892. Page 439

Lekavicius, V.; Shipkovs, P.; Ivanovs, S.; Rucins, A. (2015-02-01). "Thermo-Insulation Properties Of Hemp-Based Products". Latvian Journal of Physics and Technical Sciences. 52 (1): 38–51. Bibcode:2015LatJP..52a..38L. doi:10.1515/lpts-2015-0004. ISSN 0868-8257.

"HISTORY OF HTIW PRODUCTS". Archived from the original on 2018-08-19. Retrieved 2018-08-08.

IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 81 (2002), Man-made Vitreous Fibres (PLEASE NOTE: Some manufacturers of insulation products^[who?] have cited this volume while making erroneous claims that "IARC scientists confirm safety of mineral wool insulation". These claims are just false. The findings in this volume are not a determination of non-carcinogenicity or overall safety.)
IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 81 (2002), Man-made Vitreous Fibres, Overall evaluation, p. 339

Houghton, Matt. Sound On Sound. "What is the best density for a good, fairly wide-spectrum absorber? . . .try looking for mineral wool in the region of 45-75kg/m3." https://www.soundonsound.com/sos/oct10/articles/qa-1010-2.htm

"HISTORY OF HTIW PRODUCTS". Archived from the original on 2018-08-19. Retrieved 2018-08-08.

Lekavicius, V.; Shipkovs, P.; Ivanovs, S.; Rucins, A. (2015-02-01). "Thermo-Insulation Properties Of Hemp-Based Products". Latvian Journal of Physics and Technical Sciences. 52 (1): 38–51. Bibcode:2015LatJP..52a..38L. doi:10.1515/lpts-2015-0004. ISSN 0868-8257.