Bluebellite and mojaveite, two new minerals from the central Mojave Desert, California, USA

Abstract

7 Cl, are new secondary copper minerals from the Mojave Desert. The type locality for bluebellite is the D shaft, Blue Bell claims, near Baker, San Bernardino County, California, while cotype localities for mojaveite are the E pit at Blue Bell claims and also the Bird Nest drift, Otto Mountain, also near Baker. The two minerals are very similar in their properties. Bluebellite is associated particularly with murdochite, but also with calcite, fluorite, hemimorphite and rarely dioptase in a highly siliceous hornfels. It forms bright bluishgreen plates or flakes up to~20 mm 620 mm 65 mm in size that are usually curved. The streak is pale bluish green and the lustre is adamantine, but often appears dull because of surface roughness. It is non-fluorescent. Bluebellite is very soft (Mohs hardness~1), sectile, has perfect cleavage on {001} and an irregular fracture. The calculated density based on the empirical formula is 4.746 g cm À3 . Bluebellite is uniaxial (À), with mean refractive index estimated as 1.96 from the Gladstone-Dale relationship. It is pleochroic O (bluish green) >> E (nearly colourless). Electron microprobe analyses gave the empirical formula Cu 5.82 I 0.99 Al 0.02 Si 0.12 O 3.11 (OH) 9.80 Cl 1.09 based on 14 (O+Cl) a.p.f.u. The Raman spectrum shows strong iodate-related bands at 680, 611 and 254 cm À1 . Bluebellite is trigonal, space group R3, with the unit-cell parameters: a = 8.3017(5), c = 13.259(1) Å , V = 791.4(1) Å 3 and Z = 3. The eight strongest lines in the powder X-ray diffraction (XRD) (045,143 ,324).Mojaveite occurs at the Blue Bell claims in direct association with cerussite, chlorargyrite, chrysocolla, hemimorphite, kettnerite, perite, quartz and wulfenite, while at the Bird Nest drift, it is associated with andradite, chrysocolla, cerussite, burckhardtite, galena, goethite, khinite, mcalpineite, thorneite, timroseite, paratimroseite, quartz and wulfenite. It has also been found at the Aga mine, Otto Mountain, with cerussite, chrysocolla, khinite, perite and quartz. Mojaveite occurs as irregular aggregates of greenish-blue plates flattened on {001} and often curved, which rarely show a hexagonal outline, and also occurs as compact balls, from sky blue to medium greenish blue in colour. Aggregates and balls are up to 0.5 mm in size. The streak of mojaveite is pale greenish blue, while the lustre may be adamantine, pearly or dull, and it is non-fluorescent. The Mohs hardness is~1. It is sectile, with perfect cleavage on {001} and an irregular fracture. with no lone pair.

Lead-tellurium oxysalts from Otto Mountain near Baker, California, USA: XII. Andychristyite, PbCu2+Te6+O5(H2O), a new mineral withhcpstair-step layers

“…The other minerals first described from here (in order of description) are ottoite, Pb 2 Te 6+ O 5 (Kampf et al, 2010a) (Kampf et al, 2010b), thorneite, Pb 6 (Mills et al, 2014). It is noteworthy that all of these contain essential Te, all but two contain essential Pb, and all but four contain essential Cu.…”

The crystal structures of the mixed-valence tellurium oxysalts tlapallite, (Ca,Pb)3CaCu6[Te4+3Te6+O12]2(Te4+O3)2(SO4)2·3H2O, and carlfriesite, CaTe4+2Te6+O8

“…Although typically rare, tellurium (Te) oxysalt minerals often have unique structures, many of which have neither been determined nor synthesised (Christy et al , 2016 a ). The rate of discovery of Te oxysalts has burgeoned in the last decade, aided greatly by the discovery of new Te mineral localities, including at Otto Mountain and the Blue Bell mine in the Mojave desert, near Baker, California (Marty et al , 2010; Mills et al , 2014; Christy et al , 2016 b ) and the Masonic Mountain district mines in northern California (Kampf et al , 2018). Tellurium oxysalt compounds are continuing to grow as an area of interest, in part due to the rich structural variation of Te bonding (e.g.…”

The crystal structure of cesbronite, Cu3TeO4(OH)4: a novel sheet tellurate topology

“…Kampf, Housley, Mills et al, 2010;Kampf et al, 2016). Secondary tellurium minerals featuring two tellurium oxidation states, +IV and +VI, typically form from alteration of sulfide zones rich in tellurides under conditions of high E h and pH (Mills et al, 2014;Grundler et al, 2008). The availability of two stable oxidation states contributes to their observed diversity.…”