Summary: Cesbronite occurs at the Bambollita mine, near Moctezuma, Sonora, with a variety of other tellurites. The colour is ‘green beetle’ (R.H.S. 135-B) with a pale streak. H 3; D_meas 4·45±0·2. Crystals are orthorhombic 2 mmm with a 8·624 Å, b 11·878, c 5·872 (all ± 0·016 Å); space group Pbcn. For Z = 2 the calculated density is 4·455 g/cm³. The strongest powder lines are 5·934 (100), 3·490 (92), 4·889 (71), 2·358 (70), 2·379 (38), 1·592 (34), 2·156 (28), and 1·698 (27). Electron-probe analysis gave: CuO 50·3 %, 50·3, 49·8, 49·4; TeO₂ 39·3 %, 39·2, 38·6, 38·6. Water determined gravimetrically 11·0 %. This gives Cu₅(TeO₃)₂(OH)₆.2H₂O.

Cesbronite is pleochroic with absorption γ ≈ β ≫ α. Optically positive with 2V_γ calc. 72°; α 1·880 ‖[100], β 1·928 ‖[001], γ 2·029 ‖[010].