A granitic pegmatite.
Ref.:
- Robinson, G.W. & Wegner, R.R. (1998): Mineralogy of the Boqueiraozinho pegmatite, Parelhas, Rio Grande do Norte, Brazil. Mineralogical Record 29, 193-197.
- Beurlen, H., Da Silva, M.R.R., Thomas, R., Soares, D.R., and Olivier, P. (2008): Nb–Ta–(Ti–Sn) oxide mineral chemistry as tracer of rare element granitic pegmatite fractionation in the Borborema Province, Northeastern Brazil. Mineralium Deposita 43, 207-228.