Taos County, New Mexico

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Taos rocks. Take this sentence any way you want to, and it’s probably true. Taos Rockers wouldn’t be the same if it wasn’t located in Taos. In addition to being a cultural destination, a hotspot for the arts, and home of Taos pueblo, Taos is located within a county that contains some of the most dynamic and diverse geology in New Mexico. To check out some of the other wonderful things to see and do in Taos County, check out the official Visitors Guide to Taos. 

Overview of Taos County Geology

At the northernmost edge of New Mexico, Taos County includes the majestic mountain landscapes of the Rockies, and the amazing sunset views of the desert southwest. From almost any viewpoint in Taos, the prominent features of the landscape are the relatively flat Taos plateau, cut by the Rio Grande’s gorge, and the mountains that flank each side of the plateau – the Sangre de Cristo on the northeastern side, the Picuris Range in the southeastern side, and the Tusas and San Juan mountains on the west side of the basin.

The Taos Plateau is covered by 3- to 5-million year old basalt flows that erupted from the Rio Grande rift; remnants of the fissure and monogenetic cinder cones can be seen as far north as Fort Garland and all the way down to Albuquerque. The basalt lava flows are mostly pahoehoe. They cover young sediments of the Santa Fe group that were shed from the flanking mountains as the rift grew. The best place to see these lava flows are from the Rio Grande Gorge Bridge and along the West Rim Trail.

The mountains that flank the Taos plateau to the east were formed along prominent faults that uplifted and exposed much older rocks in the Sangre de Cristo and the Picuris ranges.

The Sangre de Cristo Mountains consist of a basement complex of Precambrian metamorphic rocks, topped by Paleozoic sedimentary rocks, and in the Red River area, intruded by Tertiary silicic igneous rocks (mostly granites) and their related extrusive volcanic rocks (mostly rhyolite and andesite). Post intrusion alteration and circulating fluids related to the Tertiary volcanism resulted in mineralization of large areas, notable the molybdenum mineralization in the Questa area. In other areas (the Moreno Valley and the Baldy Mountain areas) pyrite-gold mineralization is associated with the Tertiary igneous activity. Pegmatite and other veins associated with this phase of igneous activity cut parts of the Sangre de Cristo mountains in Taos County.

The Picuris Mountains are Precambrian in age, and consist of three major rock groups:

  • The Ortega Group - a meta-quartzite with andalusite- and kyanite-rich layers, topped by the phyllites, meta-quartzites and staurolite-garnet schists of the Rinconada Formation, which is topped by the black slate and garnet phyllite of the Pilar Formation. The Ortega group lies below the Vadito group, and the boundary has been interpreted as either a fault or an erosional unconformity.
  • The Vadito Group – the Marquenos Quartzite, overlain by a muscovite-quartz schist sequence that contains amphibolites and meta-volcanic rocks.
  • The Embudo Granite – a series of intrusive igneous rocks intruding the other groups, followed by many pegmatite dikes cutting through the sequence.

For an excellent overview of Taos County geology, you can visit the website developed by NASA in conjunction with the Johnson Space Center and the New Mexico Bureau of Geology for the training of astronauts for lunar mission. 

Mineral Collecting in Taos County

Much of Taos County is National Forest and National Park land, so collecting mineral specimens is restricted or forbidden. Other mineral-rich areas are privately-owned mining claims so collecting minerals there is also not permitted. Ownership, boundaries and conditions change frequently. For up-to-date collecting information, you can visit the Taos Rockers shop and talk to owner Cortney Stewart or staff member Jesse Kline.

The most accessible collecting site is the Harding Pegmatite – located in the Embudo Granite Group of the Picuris Mountains, this pegmatite contained significant deposits of lithium, niobium, tantalum and beryllium that led to its exploitation. Production has been intermittent since it started in 1918 and closed in 1951. The mine now belongs to the University of New Mexico; visitors must complete an application and risk-and-release form before entering the mine site – see HERE for details.

UNM also has a printed “walking tour” of the Harding Mine - click HERE. 

For more information check these sites -

Precambrian deformational history of the Picuris Mountains, New Mexico

by Kent C. Nielsen and Scott, T. E., Jr., 1979, pp. 113-120

Precambrian geology of the Picuris Range, north central New Mexico

Arthur Montgomery (1956)

 

Mining Districts and Areas of Taos County

The information in this section is from the book Minerals of New Mexico (1996), Stuart A. Northrop, 3rd edition revised by Florence A. LaBruzza. UNM Press, 346pp

Anchor district

Chalcopyrite, fluorite, gold, hematite, limonite, muscovite, petzite, pyrite, quartz

Glenwoody district

Almandine, andalusite, andradite, biotite, bismutite, cordierite, corundum, dravite, gold, grossular, kyanite, lepidolite, microcline, muscovite, paragonite, pectolite, petalite, piemontite, psilomelane, quartz, schorl, sillimanite, staurolite, vesuvianite, zoisite (thulite)

Harding Mine District

Albite, allanite, almandine, amblygonite, andalusite, ankerite, apatite, azurite, bertrandite, beryl, beyerite, biotite, bismite, bismuth, mismuthinite, mismutite, mismutotantalite, bityite, calcite, cassiterite, chalcocite, chalcopyrite, chloritoid, chrysocolla, columbite-tantalite, cordierite, danalite, elbaite, epidote, eucryptite, fluorapatite, fluorite, gahnite, holmquistite, illite, ilmenite, kaolinite, lepidolite, limonite, lithiophilite, lollingite, magnetite, malachite, manganocolumbite, manganotantalite, microcline, microlite, monazite, montmorillonite, mottramite, muscovite, oligoclase, orthoclase, petalite, pickeringite, piemontite, pucherite, pyrite, pyrolusite, pyrophyllite, quartz, roscoelite, rutile, schorl, spessartine, spodumene, tenorite, thorite, titanite, topaz, tourmaline, uranpyrochlore, vanadinite, wavellite, zircon, zoisite (thulite)

Hondo Canyon district

Andalusite, arsenopyrite, biotite, galena, kyanite, magnetite, muscovite, petalite, pyrite, pyrophyllite, quartz, sillimanite, staurolite, talc

Picuris District

Actinolite, alite, allanite, almandine, andalusite, andesine, apatite, argentite, arsenopyrite, augite, azurite, beryl, biotite, bismutite, bornite, brookite, bytownite, calcite, chalcocite, chlorargyrite, chlorite, chloritoid, chrysocolla, clinozoisite, columbite-0tantalite, conichalcite, cordierite, corundum, cuprite, cuprotungstite, danalite, diopside, dravite, epidote, garnet, gold, hematite, ilmenite, kaolinite, kyanite, labradorite, lepidolite, limonite, magnetite, malachite, microcline, muscovite, oligoclase, orthoclase, petalite, phlogopite, pyrite, pyrophyllite, quartz, scheelite, sillimanite, silver, spessartine, spodumene, staurolite, tetrahedrite, thulite, titanite, tourmaline, tremolite, volborthite, wolframite, zircon, zoisite

Red River district

Actinolite, albite, almandine, alunite, alunogen, anatase, andesine, apatite, argentite, augite, biotite, bismuth, calaverite, calcite, chalcocite, chalcopyrite, chlorite, dolomite, epidote, ferrimolybdite, fluorite, galena, gold, graphite, grossular, gypsum, hematite, hubnerite, ilmenite, jarosite, kaolinite, kyanite, labradorite, limonite, magnetite, malachite, microcline, molybdenite, monazite, montmorillonite, muscovite, oligoclase, orthoclase, petzite, pyrite, quartz, rhodochrosite, rhodonite, rutile, serpentine, sillimanite, silver, smithsonite, sperrylite, sphalerite, stibnite, titanite, tourmaline, uraninite, vanadinite, wolframite, zircon, zoisite

Twining district

Azurite, bornite, calcite, chalcocite, chalcopyrite, chlorite, copper, epidote, galena, gold, hematite, limonite, magnetite, malachite, molybdenite, pyrite, quartz, siderite, stibnite, talc, tenorite, tourmaline

Costilla area

Beryl, muscovite (fuchsite), olivine, rutile

Tres Piedras area

Augite, cristobalite, euxenite, hypersthene, olivine, samarskite

Vermejo Park

Allanite, thorogummite, zircon

 

Featured Taos County Minerals

Smoky Quartz – from the western slope of the Sangre de Cristo Mountains, these specimens are from the Cenozoic igneous rocks that intrude the Precambrian units of the Sangre de Cristo.

Zoisite, variety thulite - from the Picuris district, these specimens feature fine-grained, massive pink zoisite, related to the intrusive igneous activity of the Embudo Granite group.

Volborthite - a hydrous copper vanadate, Cu3V2O7(OH)2·2H2O, on matrix containing malachite and sometimes chrysocolla. These specimens from from the Copper Hill deposit, Picuris district, Taos Co., New Mexico.

Staurolites – the "stone of Taos," from the Picuris district, Hondo Canyon area. Although staurolite is not uncommon as a regional metamorphic mineral world-wide, the 90-degree twinned crystals found in the Hondo Canyon area of Taos County are exceedingly rare (some are also found in North Carolina and in Russia). For years, most staurolites from this locale were provided by Mr. Joe Greaves (now deceased), “Mr. Staurolite,” who owned the mining claim and oversaw the production, cleaning and setting of the crystals.