We report on a theoretical study of a new type of X-ray detector: a microcalorimeter array of paramagnetic absorber pads, operated in a strong ambient magnetic field, read out with the help of nitrogen vacancy (NV) center doped diamond crystals. The energy delivered by an impinging X-ray photon raises the temperature of one of the erbium-doped gold absorber pads. The magnetic field transient caused by the increased temperature of the absorber pad is sensed with the magnetic field sensitive NV centers. The latter are read out in the usual way by pumping the NV centers with a LASER and recording the fluorescent yield as a function of the frequency of an applied microwave field. In theory, the approach could be used to achieve extremely good (sub-micrometer) spatial resolutions, as well as good energy resolutions. We describe the general experimental setup and the components required for operating such detectors and discuss estimates of their spatial, temporal, and energy resolutions. Finally, we discuss potential applications of such detectors in X-ray astronomy.