Dadsonite was previously described without a name: (mineral Q) from Yellowknife, N.W.T.; (mineral QM) from Madoc, Ontario, and Pershing County, Nevada. Material from a fourth locality (Wolfsberg, Germany) yields good powder patterns, identical with those of QM, and single crystal data identical with those for Q.

Microprobe analysis of the Nevada and Wolfsberg samples gave, respectively, Pb 49·3, 50·8; Sb 31·7, 31·8; S 20·7, 20·3; sum 101·7, 102·9 %, giving Pb₁₁Sb_12·0S_29·8 and Pb₁₁Sb_11·7S_28·4, ideally Pb₁₁Sb₁₂S₂₉ or 11PbS·6Sb₂S₃. Dadsonite is acicular [010], monoclinic, space group P2, Pm, or P2/m, with a 19·05, b 4·11, c 17·33 Å, β 96° 20′, Z = 1, Sp. gr. 5·76. The strongest lines of the X-ray pattern are 3·78 (7), 3·62 (6), 3·38 (10), 2·84 (7), and 2·79 Å (6).