The SagaB biotite is a crystal that was collected by one of the authors (JG) in 2017 in remnants of a commonly inundated, large, nepheline-bearing syenite pegmatite body in the former Saga 1 larvikite quarry (59.0439° N, 9.8289° E), Sagåsen, Porsgrunn, Norway. The pegmatite is extremely coarse grained, with dm-sized biotite crystals, and has, in places, gradational contacts to the host larvikite (an alkali monzonite). Formation of the pegmatite body is thus expected to be late-magmatic with respect to its host intrusion that is dated by U-Pb zircon and baddeleyite ages of 293.2 +/-1.3 and 294.3 +/-1.2 Ma, respectively. 32