[3] This extended formula shows the presence of cyclic silicate groups and dominance of Si at the M4 site, according to the nomenclature of the eudialyte group.

[2] Kentbrooksite was found in alkaline pegmatites within pulaskites of the Kangerdlugssuaq intrusion in East Greenland.

[3] Rare earth elements (REE) in kentbrooksite are dominated by cerium and yttrium.

Potassium, strontium, iron, aluminium, titanium, magnesium are present as other admixtures.

An important fraction of fluorine is substituted by chlorine and hydroxyl groups.