Arendalite (of Blumenbach)

A synonym for epidote from the Arendal iron mines in Norway, which occurs in well-developed green crystals.

The history of the mineral name is interesting:
The name "Arendalit" seems to appear first in Blumenbach (1799). It may have been coined by the Dane Peter Christian Abildgaard around 1800. One year later, it appears in Karstens (1800). "Arendalit" referred to large six-sided greenish crystals that were found at the Arendal iron mines, Norway (thus the name Arendalite). These were first described in 1794 by Widenmann as "Ein noch unbekanntes Fossil [Another unknown fossil]", but given no name by him. Abildgaard sent some samples to the French mineralogist Haüy who responded that it was related to thallite (of Delamétherie 1792; a synonym of epidote). Later, Abildgaard (1801) described the mineral as "arendalischen thalit, oder der sogennannten Arendalit". Samples from Arendal were among the samples Haüy studied when he coined the name epidote, and he described the epidote from Arendal as "le plus parfaits que j'ai observés [the most perfect ones I have observed]".

* Karsten (1800) is cited in various books, but he refers to Blumenbach (1799) who, in turn, refers to an analysis in Gmelin (1798).

This usage has also occasionally been used for epidote from other localities (i.e. the Harts Range, NT, Australia; see https://www.mindat.org/mesg-496526.html#572233 ).