[4] It is the third eudialyte-group mineral with essential tungsten (after khomyakovite and manganokhomyakovite), and second with essential rare earth elements (after zirsilite-(Ce),[2] which is the niobium-analogue of johnsenite-(Ce)).
[3] Other characteristic feature is the presence of essential carbonate group, shared with carbokentbrooksite, golyshevite, mogovidite and zirsilite-(Ce).
[2] Johnsenite-(Ce) was discovered in alkaline rocks of Mont Saint-Hilaire, Quebec, Canada, which is also a type locality for other eudialyte group species: oneillite, khomyakovite and manganokhomyakovite.
[5] The association of johnsenite-(Ce) is rich, as it includes aegirine, albite, amphibole-group mineral, burbankite-group mineral, calcite, catapleiite, cerite-(Ce), dawsonite, epididymite, fluorapophyllite, galena, microcline, molybdenite, natrolite, pectolite, pyrite, pyrrhotite, quartz, rhodochrosite, sphalerite, steacyite, stillwellite-(Ce), titanite, tuperssuatsiaite, zakharovite and zirsilite-(Ce).
[3] Notable impurities in johnsenite-(Ce) are iron, titanium, niobium, yttrium, potassium, praseodymium, and neodymium.