A New Mineral Species from Maine!

Fig. 1: MP2 Research group in the field

The tenth new mineral species from Maine, tantalowodginite, which was described by MMGM’s MP² Research group (Fig. 1), was approved by the International Mineralogical Association (IMA) in January!  The type location is the Emmons pegmatite in the town of Greenwood where it occurs as composite crystals. Tantalowodginite (reddish-brown) typically grows over a member of the columbite-tantalite group (black) and is over-grown by wodginite (black) or by a columbite-tantalite mineral.

The wodginite group consists of several members: wodginite (MnSnTa₂O₈), ferrowodginite (FeSnTa₂O₈), ferrotitanowodginite (FeTiTa₂O₈), lithiowodginite (LiTa₃O₈) and tantalowodginite ((Mn_0.5□_0.5)TaTa₂O₈). Wodginite is the most common. Among its many occurrences world-wide, four are in Maine. All of the other members are rare.

Ray Sprague and Tony Wielkiewicz (Mongort Minerals) discovered the first specimens during mining operations at the Emmons quarry in 1997.  As simple as the composition of tantalowodginite is, the crystal structure determination was difficult and has caused decades of delay in completing the study. Here is the formal notification published by the International Mineralogical Association:

IMA No. 2017-095 Tantalowodginite (Mn_0.5□_0.5)TaTa₂O₈ Emmons pegmatite dike, exposed on Uncle Tom Mountain, Greenwood, Oxford Co., Maine, USA (44°19’24”N, 70°41’41”) Sarah L. Hanson, Alexander U. Falster, William B. Simmons, Raymond Sprague, Pietro Vignola*, Nicola Rotiroti, Sergio Andó and Frédéric Hatert *E-mail: pietro.vignola@idpa.cnr.it Wodginite group Monoclinic: C2/c; structure determined a = 9.542(1), b = 11.488(2), c = 5.128(1) Å, β = 91.13(1)° 7.332(20), 4.741(20), 3.838(30), 3.667(100), 3.000(100), 2.957(100), 2.883(30), 1.778(30)  Type material is deposited in the mineralogical collections of the Maine Mineral and Gem Museum, 99 Main Street, Bethel, Maine, USA, catalogue number MMGM-MP2-12-10-2016

Fig. 2: Tantalowodginite with wodginite rim. 12 cm maximum dimension. Emmons Mine Collection.

Fig. 3: Freshly exposed cross section of tantalowodginite (reddish-brown) with thin black wodginite rim and black manganotantalite core.  7 cm across.