Carbokentbrooksite
Carbokentbrooksite is a very rare mineral of the eudialyte group, with formula (Na,[])12(Na,Ce)3Ca6Mn3Zr3NbSiO(Si9O27)2(Si3O9)2(OH)3(CO3)H2O. The original formula was extended to show the presence of cyclic silicate groups and silicon at the M4 site, according to the nomenclature of eudialyte group. Carbokenbrooksite characterizes in being carbonate-rich (the other eudialyte-group species with essential carbonate are zirsilite-(Ce), golyshevite, and mogovidite). It is also sodium rich, being sodium equivalent of zirsilite-(Ce), with which it is intimately associated.