Cannonite, Bi20(OH)2S04, a new mineral from

Cannonite, ideally Bi20(OHhS04 ' is a new mineral from the Tunnel Extension mine, Ohio Mining District, Marysvale, Utah, USA. It occurs mostly as intergrown crystalline aggregates «I mm) of subhedral to euhedral equant to prismatic crystals «200 [Am)in cavities in quartz gangue. Other associated minerals arc cuprobismutite, bismuthinite, and covelline. Cannonite is colour]ess and transparent with an adamantine lustre and white streak. It is brittle with an uneven to conchoidal fracture. In reflected light it is low reflecting, weakly to moderately bireflectant and weakly anisotropic. Internal reflections (colour]ess to white) are abundant. Measured reflectance values in air and oil are tabulated. Colour values relative to the CIE illuminant C for R I and R2in air respectively are: Y % 10.4, 11.7; Lambdad 475, 475; P,, % 2.6,3.0. Calculated refractive indices at 589 nm: RJ 1.91 and R2 1.99. YHN 11I0229 (range 183-280); calculated Mohs hardness is 4. X-ray studies show that cannonite is monoclinic with space group nIle and a 7.700(3), b 13.839(6), e 5.686(2) A, [3 109.1l(3t. It has a cell volume of 572.5(4) A ' with Z 4. Dcal,,-,-is 6.515 g/cm3. The strongest six lines of the X-ray powder pattern are [d in A (I) (hkl)] 3.206 (100) (221); 1.984 (90) (340, 152); 2.924 (70) (13]); 3.644 (60) (Ill); 3.466 (60) (040); 2.782 (50) (Il2). Averaged probe analyses gave the empirical formula Bil.yyO(OHI.04hSo.yy04 on the basis of 7 oxygen atoms. The name is fo