[3] It occurs in association with uraninite, thorite, pyrite, marcasite, roscoelite, clay minerals and amorphous organic matter.

[9] Recent electron microprobe analysis of the submicroscopic crystals uncovered an abundance of calcium, yttrium, phosphorus, and minimal lead substitutions along with traces of other rare earth elements.

[16] Stieff et al. analyzed coffinite using the x-ray powder diffraction technique and determined that it has a tetragonal structure.

[8] Occurring naturally with U4+ cations, the UO8 triangular dodecahedra coordinate with edge-sharing, alternating SiO4 tetrahedra in chains along the c-axis.

[15][13] Initial examination of coffinite by Stieff et al. described the mineral as black in color with an adamantine luster, indistinguishable from uraninite (UO2).

[8] Later samples from Woodrow Mine in New Mexico collected by Moench showed fibrous internal structure and exceptional crystallization.

[11] In vein deposits of the Copper King Mine in Colorado, coffinite was also found to occur with uraninite and pitchblende.

[9] Coffinite and uraninite precipitate inside brecciated and fractured regions of altered granite at pressures between 500 and 800 bars and temperatures at 126 to 178 °C.

[6] Researchers at Harvard University, the United States Geological Survey (USGS), and several other institutions attempted unsuccessfully to synthesize coffinite in the mid-1950s after its initial discovery.