BROCHANTITE, LINARITE & FLUORITE: BLANCHARD MINE

 

As noted in previous postings, Rebecca Nohe Estate Sales dispersed the rock and mineral collection of longtime Colorado Springs Mineralogical Society member Laurann Briding.  The sale attracted a large number of buyers wearing masks who were admitted via reservation (due to Covid-19 pandemic).  I came home with a few interesting specimens described in Postings on August 12 and 13. In addition, I have several Briding micromounts (~70) that were purchased at this sale, and at a later cleanup sale.  Among these mounts were several from the Blanchard Mine, New Mexico, and the subject of this Posting.

Dealers offering minerals “for sale” in many Colorado shows often display numerous chunks of fluorite. More than likely the larger hunks are labeled “Blanchard Blue” the signature mineral mined from the Blanchard Group mines (and associated Mex-Tex, Desert Rose, and Royal Flush Groups of mines), Hansonburg District, Socorro County, New Mexico.  These mines are associated with activity in the Rio Grande Rift System (Colorado And New Mexico terminology), part of the Great American Rift System that extends from Mexico north along the Rocky Mountain Front to north central Colorado (and perhaps further).  The Rio Grande River flows in the Rift System in New Mexico and southern Colorado while the upper reaches of the Arkansas River travel through the central part of Colorado. Movement of magma under the rift and release of crustal pressure most likely was responsible for this rift.

The Hansonburg Mining District is located in the Sierra Oscura Mountains near the tiny community of Bingham, New Mexico, on the eastern edge of the southern section of the rift system.  The District is one of approximately 30 barite-fluorite-galena deposits in the southern New Mexico part of the Rio Grande Rift (Rakovan and Partey, 2009). The basement rocks in the Mountains are composed of Proterozoic granites and gneisses while Pennsylvanian marine rocks and arkose overlay the Precambrian rocks and host the mineralization.  Evidently the hydrothermal fluids containing the minerals migrated from deep within the Jornada del Muerto Basin under-lying basement rocks to the west of the Hansonburg District (Rakovan and Partey, 2009).  

As for mineable metallic minerals it seems as if hard rock miners could not make a living from galena (lead), barite, or copper; however, many secondary and gangue minerals are of great interest to collectors and there are several specimen mines in the area. Perhaps the best known of the collectables is Blanchard Blue fluorite, specimens of which are found at hundreds of rock and mineral shows, especially in the southwest U.S.  Other “famous” collectables are the “world’s largest linarite crystals” [PbCu(SO₄)(OH)₂] (Delventhal, 2018). and colorful brochantite [Cu₄(SO₄)(OH)₆].

Crystals of linarite with submillimeter clear crystals of cerussite scattered about. Goethite "crust" noted on top specimen.  Width of both specimens ~7 mm.

Small cubes of clear fluorite with larger light tinted modified crystals of fluorite along with some quartz, what appears to be tiny cerussite crystals, sprays of brochantite sticking up in left bottom corner, and who knows what the material in lower right corner is.  Width FOV ~9 mm.

The handwritten note with the nine Briding micromounts states: “glory hole Blanchard cc bought 1968 fr Tony. linerite (sic),  malachite, fluorite, brochantite, barite, azurite.” I do not believe azurite is present and the blue specimens are linarite.  In addition, the bundles of green acicular crystals are probably brochantite rather than malachite.  There also are some nice gemmy, elongated, and striated crystals of cerussite.

 Brochantite sprays of acicular crystals.  Width of specimen ~5 mm.

Two cerussite crystals in center at a 45 degree angle pointing towards upper right corner.  Several smaller sprays of acicular brochantite. Width FOV ~7 mm.

A spray of green acicular brochantite and bundles of green and colorless brochantite. Cerussite lining right margin.  Maximum width of specimen ~7 mm.  

Sprays of prismatic brochantite of goethite.  Width FOV ~7 mm. 

This was originally identified as malachite but these are bundles of dark green brochantite on barite. Width FOV ~6 mm.

 

Sprays of brochantite on barite.  Width FOV ~7 mm.

Prismatic brochantite attached to goethite. Width of specimen ~ 6 mm.

Sprays of colorless and green acicular brochantite. Width FOV ~7mm.

Two other perky boxes came with the nine micromounts but are more macromounts than micro; however the specimens are mounted on posts with appropriate labels: 1) “Fluorite, clear xyls, Blanchard Claims, NM;” 2) “fluorite, quartz, pyrite, Blanchard Claims, N.M. Koelin.”  Now, I don’t have the slightest idea about the word Koelin.  Perhaps some reader will recognize the term as the “collector”? 

Mixture of transparent fluorite, mostly cubes.  Width FOV ~ 1.0 cm.


 

Mixture of blue to clear fluorite cubes, nice terminated quartz crystals.  The quartz in some areas is tinted sort of a light reddish brown. The faded yellow blogs are some sort of a clay mineral (I presume). The middle photo has a couple of pyrite crystals. Width FOV ~1.0 cm.
      

 

REFERENCES CITED

Delventhal, E., 2018, The Blanchard Mine, Hansonburg District, Socorro County, New Mexico: Minerals of the Metallic Ore Deposits of the American Southwest Symposium, August 4 - 5, 2018, Colorado School of Mines Campus, Golden, Colorado.

Rakovan, J., and F. Partey, 2009, Mineralization of the Hansonburg Mining District, Bingham, New Mexico: New Mexico Geological Society Guidebook, 60th Field Conference, Geology of the Chupadera Mesa Region.