Third Worldwide Occurrence of Juangodoyite, Na2Cu(CO3)2, and Other Secondary Na, Cu, Mg, and Ca Minerals in the Fore-Sudetic Monocline (Lower Silesia, SW Poland)

Łukasz Kruszewski,Mateusz Świerk,Eligiusz Szełęg,Rafał Siuda,Beata Marciniak-Maliszewska

doi:10.3390/min10020190

Abstract

Na-Cu carbonates are relatively rare secondary minerals in weathering zones of ore deposits. Hereby we describe mineral composition and crystal chemistry of the most important secondary (Na)Cu minerals and their Na- and Mg-bearing associates forming rich paragenesis in Rudna IX mine. A non-bulky Ca-rich dripstone-like paragenesis from Lubin Główny mine is also characterized, using Powder X-Ray Diffraction, Rietveld, and Electron Microprobe methods. Light blue juangodoyite (3rd occurrence worldwide) and darker chalconatronite are the most important members of the Rudna IX paragenesis, being associated with malachite, aragonite (intergrown with hydromagnesite and northupite), and probably cornwallite. Most of the minerals are chemically close to their ideal composition, with minor Mg substitution in malachite. Cu chlorides are mainly represented by clinoatacamite and probably herbertsmithite. Additional, minor phases include trace Cu minerals langite, wroewolfeite, and a lavendulan-group mineral, and monohydrocalcite. Separate halite-rich encrustations are shown to be filled with eriochalcite, ktenasite, and kröhnkite. The most likely to be confirmed coexisting species include paratacamite, wooldridgeite/nesquehonite, johillerite, melanothallite, and kipushite. The Lubin paragenesis mainly comprises aragonite, gypsum, rapidcreekite, and monohydrocalcite, with trace vaterite. Blue colouration is mainly provided by a yet unspecified Ni-, Co-, Mg-, and Mn-bearing Cu-Zn-Ca arsenate mineral close to parnauite.

Highlights

Juangodoyite, Na2 Cu(CO3 )2, is an exceedingly rare mineral, known—prior to the current study—from a single locality in Chile: Santa Rosa mine, Iquique Province [1]. It is the natural equivalent of sodium di(carbonato)cuprate(II), named to honour Juan Godoy—the discoverer of the famous Chilean silver occurrence at Chañarcilllo
The synthetic equivalent of juangodoyite is obtained as small pinacoids, with dimensions ~0.1 mm, slightly elongated along the c axis, and somewhat irregular [2]
Both dark dolomite samples and white sandstone samples from the Rudna IX mine are covered by rich accumulations (Figure 3) comprising:

Summary

Introduction

Juangodoyite, Na2 Cu(CO3 ) (monoclinic, P21 /a), is an exceedingly rare mineral, known—prior to the current study—from a single locality in Chile: Santa Rosa mine, Iquique Province [1]. It is the natural equivalent of sodium di(carbonato)cuprate(II), named to honour Juan Godoy—the discoverer of the famous Chilean silver occurrence at Chañarcilllo. The hydrated, or trihydrate, counterpart of juangodoyite—chalconatronite (monoclinic, P21 /n)—is more common, with about 20 localities worldwide. Minerals 2020, 10, 190 by Mosset et al [3]. A second occurrence of juangodoyite, within drainage-related mine speleothems (minothems) of the Libiola Mine, Italy, was reported in Reference [4]

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Results

Conclusion