A mafic, coarse-grained apatite-rich enclave found in the High Tatra granite, Western Carpathians, is an ultrapotassic rock with mixed (mantle-crustal) geochemical and mineralogical signatures. A U-Pb zircon age dates the intrusion at 345±5.1 Ma. Zircon cores preserve ages of 361±7.6 Ma and 391±4.6 Ma. The apatite-rich rock could be interpreted as a cumulate material related to common Tatra granite of comparable age (360–340 Ma). This rock, of very unusual mineralogy, is an atypical cumulate formed in rocks of granitoid composition.