trigonite

trigonite

[′trī·gə‚nīt]
(mineralogy)
MnPb3H(AsO3)3 A sulfur yellow to yellowish-brown or dark brown, monoclinic mineral consisting of an acid arsenite of lead and manganese; occurs in domatic form.
References in periodicals archive ?
I'm sure that many readers of their new book will be agreeably surprised to find that not only are these minerals chemically interesting, they are often very beautiful as well: raspberry-red sarkinite globules, deep purple allactite, bright yellow trigonite in simple triangular plates, and some of the prettiest nadorite crystals you ever saw, adamantine yellow on their black matrix.