Summary: An occurrence of magnesian collinsite has been found with other rare phosphates in a variscite deposit in semi-desert 15 km NW. of Milgun Station homestead (25° 6′ S., 118° 18′ E.), Western Australia. The collinsite occurs as tapering white 3-mm prisms, mammillated aggregates, and thin veinlets in cavities in mudstone. The crystals have two good cleavages, D2.93, subvitreous lustre, H4–5, white streak and are brittle. Optical properties α 1·632, β 1·642, γ 1·657, 2Vγ , ≈ 80°. The mineral is triclinic with a 5·734, b 6·780, c 5·441 Å, α97·29° β 108·56°, γ 107·28°. X-ray powder data given, the lines are similar to P.D.F. card 14–314 but new cell gives better indexing. Chemical analysis by F. R. W. Lindsey gave FeO 0·07, MgO 11·3, CaO 35·2, Na₂O 0·01, K₂O 0·02, P₂O₅ 41·2, H₂O⁺10·7, H₂O⁻ 0·15, F 0·02, SiO₂ (quartz impurity) 1·31, Al, Mn, Zn, SO₃ not detected, net sum 99·97, close to Ca₂Mg(PO₄)₂.2H₂O, after deduction of moisture and quartz impurity. Typical specimens are preserved at the Government Chemical Laboratories, Perth, Western Australia.