Merumite; a complex assemblage of chromium minerals from Guyana

Abstract

TABLE 3. Spectrographic analyses (in percent) of four merumite samples _ 9 4. X-ray powder patterns of merumite (eskolaite 37 percent, guyanaite 63 percent), merumite approaching eskolaite (Guyana), guyanaite (Guyana, four strongest lines), eskolaite (Finland), and Cr2O8 9 5. Cell constants of guyanaite (from Guyana and Finland), and of CrOOH, ScOOH, and InOOH 11 6. Analyses of guyanaite ______________________-_ __________ ______________ ____ _____ _ 12 7. X-ray powder data of (Cr, Al, Fe, Ti, Mn)02 from guyanaite, and CrO2 from CrOOH _ 8. X-ray powder data of (Cr, Al, Fe, Ti Mn) 2O8 ____-_ _ 9. X-ray powder data of guyanaite (from Guyana and Finland), "merumite" and synthetic guyanaite CrOOH 10. Analysis of merumite containing 70 percent bracewellite and 30 percent eskolaite ______ _____ __ _ 11. Spectrographic analysis of merumite containing 70 percent bracewellite and 30 percent eskolaite _ ______ 12. Electron-probe analysis (in percent) of seven crystals of bracewellite and two merumite fragments ______ 13. X-ray powder data for bracewellite, goethite, and eskolaite ___________ __ __ __ __ _ ___ 14. Chemical analysis of grimaldiite-mcconnellite polycrystals _______ _________________ ____ __ ___ 18 15. Microspectrographic analysis of grimaldiite-mcconnsllite polycrystals _____ __ _ _ __ __ ____ _ 16. X-ray powder pattern of grimaldiite and mcconnellite ___________ __ __ __ __ _ ____ __ 17. Cell constants of grimaldiite, mcconnellite, and related substances ______ ______ __ _____ ___ 18. X-ray powder patterns of 7-CrOOH and lepidocrocite ________ _____________ 19. Cell constants of 7-CrOOH and related compounds ___ __ __ ______ ______________ _ ____ ___ 20. X-ray powder data for chromian gahnite Zn(Al0.7, CrOo.sHOi from Guyana and synthetic spinels ________ 23 21. Gold and silver in six fragments of merumite ___ ____ ____ ____ _ 22. X-ray powder data for topaz _____________________________________ __ 23. Analysis of topaz _________________________________________________ ______ 26 24. Crystallographic relationship of the CrOOH compounds and other metallic hydroxides _____ ______ 27 MERUMITE A COMPLEX ASSEMBLAGE OF CHROMIUM MINERALS FROM GUYANA

Long-range vs. short-range ordering in synthetic Cr-substituted goethites

“…Bracewellite, CrOOH (Milton et al, 1976) is isostructural with goethite. The surface of goethite may be include attached Cr(III) ions which were released from Cr-bearing minerals during weathering.…”

Effects of common groundwater ions on chromate removal by magnetite: importance of chromate adsorption

“…A distance (2.98 Å), which is consistent with edge of two MeO 6 polyhedral with Me as Fe and or Cr, was reported in the XAS analysis of Cr(III) surface precipitates (γ-CrOOH) in ferrihydrite at pH 4 [ 43 ]. Feff/XRD generated Cr–Cr interatomic distance in bracewellite, CrO(OH), at 2.97 Å [ 44 ].…”

Cr-Fe metacolloidal nodules from the white carnallite rocks of the Verkhnekamskoe salt deposit

“…Îêñèãèäðîêñèäû õðîìà âñòðå÷àþòñÿ åùå ðåaeå. Íàèáîëåå èçâåñòíûå èç íèõ íàéäå-íû â Ðåñïóáëèêå Ãàéàíà, ãäå â ñîñòàâå ýêçîòè÷åñêîé ïîðî-äû ìåðóìèòà áûëè îáíàðóaeåíû òðèãîíàëüíûé è ðîìáè-÷åñêèå ïîëèìîðôû CrO(OH) -ãðèìàëüäèò, áðåñóýëëèò è ãâèàíàèò, àññîöèèðóþùèå ñ ýñêîëàèòîì (Cr 2 O 3 ), ìàêêî-íåëèòîì (CuCrO 2 ), õðîìèñòûì ãàíèòîì (Zn(Al,Cr) 2 O 4 ), ïèðîôèëëèòîì è ñàìîðîäíûì çîëîòîì [19]. Âñå ýòî äà-ëî îñíîâàíèå îáúÿñíèòü îáðàçîâàíèå îêñèãèäðîêñèäîâ õðîìà ãèäðîëèòè÷åñêèì ðàçëîaeåíèåì õðîìñîäåðaeàùèõ ìèíåðàëîâ â ãèïåðãåííûõ óñëîâèÿõ.…”