Mineral · Phyllosilicate
Prehnite
Ca2Al2Si3O10(OH)2
Prehnite is the pale green to yellow botryoidal mineral of basalt cavities and Alpine clefts, famous from Mali (with epidote), the New Jersey traprock quarries (Paterson, Prospect Park), Quebec's Jeffrey Mine and Australia's Wave Hill. It is the first mineral named after a person (Colonel Prehn, 1788). Prehnite 'fingers' and casts after anhydrite from New Jersey are the American classics.
| Formula | Ca2Al2Si3O10(OH)2 |
|---|---|
| IMA status | grandfathered |
| Crystal system | Orthorhombic |
| Mohs hardness | 6–6.5 |
| Group | Phyllosilicate |
| Type locality | Karibib, Namibia (historical) |
| Streak | White |
| Specific gravity | 2.9 |
| Reference list | IMA List of Minerals (RRUFF) — verify formula and status against the current list |
Elsewhere
Cite this article
Stratum Strata. "Prehnite" (Mineral). Stratum Strata pack 2026.09, as of 2026-09-21. https://stratum.black/strata/minerals/prehnite. Accessed 2026-09-21.
@misc{stratum-prehnite,
title = {Prehnite},
author = {{Stratum Strata}},
howpublished = {\url{https://stratum.black/strata/minerals/prehnite}},
year = {2026},
note = {Mineral article, Stratum Strata pack 2026.09, as of 2026-09-21; sources: stratum, wikidata, commons. Accessed 2026-09-21.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.