The here characterized biotite from Phalaborwa (23.99°S, 31.13E, RSA) is separated from a boulder of biotite apatitite. The rock is coarse-grained, with crystals of apatite up to 5 cm and biotite up to 2 cm in diameter, has an igneous-pegmatitic appearance with absence of ductile deformation textures combined with presence of cm-sized rounded xenoliths of fine-grained, blackish mafic rock. The biotite is homogeneously reddish-brown, whereas the apatite is greenish and transparent, indicating that no post-crystallizational overprint occurred. The Rb-Sr age can thus be expected to be identical to the magmatic intrusion age of the Phalaborwa main phoscorite (2062 +/-2 Ma 29 )