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Nosean is a common constituent of rocks of the district, including phonolite, plagioclase phonolite, and tephriphonolite.
The predominant crystal form for all four species is the dodecahedron, as illustrated by the nosean crystal on biotite in Figure 2 and the beautiful, blue hauyne crystal in Figure 3.
The four species have an amazing propensity to form twins such as those of sodalite from Monte Somma, hauyne from Mendig in the Eifel District, and nosean from the Alban Hills shown in Figures 6-8, respectively.
Typical examples are those in Figures 6-8, showing beautiful, elongated twins of sodalite, hauyne and nosean, respectively.
Returning now to real crystals, fine examples of twinned nosean crystals with modifying cube faces from Mendig are shown in Figures 10 and 11.
Also obtained by exchange from one or several of these localities are many other rare and interesting species such as superb danburite, nosean, afghanite, transparent allanite, tadzhikite-(Ce), green thorite, urano-thorianite, asbecasite, stillwellite-(Ce), transparent brown baddeleyite, tiny red-brown crystals of betafite, very small, dark brown crystals of zirconolite-3T, and beautiful, greenish yellow, transparent crystals of vicanite-Ce.
The very nice zircon specimen shown in Figure 4 also shows excellent, twinned nosean crystals plus a jet-black, very sharp allanite crystal on the reverse side.