GALENA WITH SIDERITE ON QUARTZ
ABOUT THE SPECIMEN
Very fine visuals on this cabinet combination specimen from the famous Alston Moor. A group of very attractive, modified cubic galena crystals to 3.2 cm on edge make up the focal point. They have a nice silver color and are well-formed all the way around. Sparkly quartz crystals serve as the backdrop, covering essentially the entire frontside of the host rock and further accented by tan to brown crystals of siderite. Together it all comes together to make for a much more intriguing and aesthetic than is typically seen for a galena matrix specimen. This piece has been sawed on the bottom to make it easily displayable, and it really does stand out as an exceptionally handsome and artistic ensemble. Formerly in the collection of Al and Sue Liebetrau.
VIDEO
MORE INFO
Alston Moor sits within the North Pennine Orefield's fluorite zone, where Pb-Zn-Ba-F mineralization formed approximately 297-294 Ma during early Permian transtensional deformation coeval with Whin Sill emplacement. Mines like Smallcleugh, Rampgill, and Brownley Hill exploited hydrothermal veins and "flat" deposits - stratabound replacements in Carboniferous Great Limestone where acidic fluids dissolved carbonate, creating horizontal cavities filled with sulfides. Galena occurs as steel-gray cubic and modified cuboctahedral crystals reaching 2 cm, often intergrown with lustrous sphalerite, ankerite, and quartz. What distinguishes Alston Moor is the abundance of flat deposits that yielded cavity specimens rather than typical vein material; crystals formed unattached in open spaces show sharper faces and better luster than crushed vein ore. The 1970s represented the golden age for collector access when abandoned mines contained untouched pockets, though systematic specimen hunting has since depleted easily accessible material. The orefield's mineralization was driven by convective fluid circulation above the concealed Weardale Granite batholith at depth, creating the characteristic concentric zoning from central fluorite-dominated zones to peripheral barite. Mining ceased in 1999, and deteriorating underground workings now limit specimen recovery from this classic English locality.