Dollaseite-(Ce)

The mineral provisionally named "magnesium orthite" by Geijer himself was renamed after structural refinement by Peacor and Dunn in 1988 led to its proper classification. The name dollaseite-(Ce) was chosen in honor of Wayne Dollase, who performed broad research on epidote minerals. The original confusion of the mineral's composition was because of a complex atomic composition where an exchange of cations leads to a form of dollaseite-(Ce) that at first glimpse resembles an Mg analogue of allanite, now known as dissakisite-(Ce). == Composition ==

With a general formula for the epidote group of A2M3Si3O13H dollaseite-(Ce) received its formula of based on data from electron microprobe analytical procedures. The results give the empirical formula (Ca.91 Ce.45 La.20 Nd.20 Pr.09 Sm.08 Gd.06)(Mg1.81 Fe.25)Al.97 Si3.0(OH)1.25 F.88 O10.99 from which the standard formula is then derived after applying Levinson’s rules for renaming REE minerals. == Structure ==

The atomic structure of dollaseite-(Ce) can be somewhat complex at times due to the charge-coupled substitution involving both cations and anions:  +  =  + . The average epidote-group mineral’s structure has chains of edge-sharing octahedral such as Al3+, Fe3+, Mn3+. The cavities that are formed by the octahedral chains that are occupied by A(1) and A(2) cations are occupied by Ca2+ and its REE, Ce3+. Similar to the other epidote-group minerals, dollaseite-(Ce) is monoclinic and thus is part of the space group P21/m. Peacor and Dunn (1988) refined the lattice parameters of dollaseite-(Ce) and concluded that the parameters were a=8.934(18) Å, b=5.721(7) Å, c=10.176(22) Å. == Geologic occurrence ==

Dollaseite-(Ce) can generally be found in mineralized dolomite-tremolite rocks in the form of dark brown and subhedral crystals. Dollaseite-(Ce) can occur in a number of locations, but the most prominent is at Östanmossa, Sweden. The type of dollaseite-(Ce) that can generally be found at this location tends to be iron-poor and occurs in tremolite skarn. The fact that dollaseite-(Ce) can be prominently found in Sweden comes as no surprise since Sweden has been known to host many REE epidote-group minerals such as dissakisite-(Ce) and allanite-(Ce). Another dollaseite-(Ce) specimen with composition slightly similar to that of dissakisite-(Ce) can be found in rock composed of fluorite and fluorian phlogopite. == See also ==