In 1949 he returned to Cambridge University as a Lecturer and as Museum Curator in Tilley's Department. He carried on with his work in laterites and widened his interest to calcareous rocks. With the collaboration of J. V. P. Long, Agrell began using the
electron microprobe to study rocks and minerals. He took in hand an extensive but ill-organised collection of
meteorites in the museum and from his study with the electron probe discovered the "Agrell effect", the decrease in the nickel content of
kamacite as a boundary with
taenite is approached. In 1962 Agrell was appointed visiting professor on the
American Geological Institute scheme. For two and a half years he was busy with Professorships at the
University of Minnesota and at
Berkeley and occasional field trips. One of these field trips took him to a road-side quarry on Highway 101 just south of Laytonville California. The local mineralogists superficially thought that the minerals were ordinary amphiboles. Agrell realized that the optics were wrong for that, and soon found that he had three new mineral species to name. Three of his colleagues at Cambridge and Manchester,
Deer,
Howie and
Zussman had just published a famous five volume set called
The Rock Forming Minerals so each of the authors got one of the minerals named after them. Playfully named, deerite was the mineral found with each of the other two, "but the junior author's minerals, howieite and zussmanite, never occurred together". (Reference: see published paper, below.) His work on meteorites and expertise in mineralogy led to him being accepted as a Principal Investigator for the investigation of lunar surface samples collected during
Apollo 11, and as the only non-American petrologist of the preliminary examination team at
Houston. Agrell's papers are archived in the
Sedgwick Museum. ==Family==