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Mt. Antero

*** During the summer months (late-June to mid-September). Much of Antero is under claim! ***

General Info

The highest North American gemstone locality at 14,245 ft, it is 10 miles southwest of Buena Vista. It is also the top phenakite location in the US. If you go, be cautious of the high elevation. Lightning storms, hail, and dehydration can hit quickly.

Minerals

Click on the image(s) below to see a picture of that mineral from this location.

Albite - One of the most common minerals on Mt. Antero, it can be found as pearly-white crystals up to 0.5 inch, according to Jacobson. Also occurs as the albite variety called cleavelandite. Associated with microcline, smoky quartz, muscovite, bertrandite, fluorite and phenakite.

Amethyst - Jacobson reports smoky quartz with amethystine tips and interiors. He also talks about amethyst crystals with a white quartz layer on the tips.

Apatite - Rarely found in the Mt. Antero region, Jacobson mentions a few people have found small clear, white and pink crystals up to 0.5 inches in diameter.

Aquamarine - Color ranges from blue to green to clear, and even pink and yellow have been found. Can sometimes be found as float within the talus boulders. The best crystals are found in the miarolitic cavities where they were formed. Murphy and Modreski (2002) say that matrix specimens are rare. Longest crystals are 7 inches, according to Jacobson.

Bazzite - Jacobson reports that blue microcrystals, up to 1/32 inch, were found in pocket sand. They were single or twinned crystals and were associated with bertrandite.

Bertrandite - Flat, white rectangular blades with striations on one face, up to nearly an inch long. Jacobson says that "heart-shaped twins are not rare." Associated with beryl, phenakite, quartz, albite and adularia.

Beryl - Mostly blue and blue-green in granite matrix, although other colors are common, such as yellow, green, colorless, and pink. In massive or crystalline form. The longest crystals recorded as of 1993 were the two 7-inch long crystals found by Ed Over in 1932. Associated with many minerals, including fluorite, smoky quartz, topaz, and phenakite.

Biotite - Blades up to a foot across are reported by Jacobson.

Bismuthinite - Only one report of bismuthinite (a pseudomorph after bismutite) was mentioned by Jacobson. It was a dark green fragment that was associated with bismutite. Other associations were quartz, microcline and phenakite.

Bismutite - Grayish or yellowish-green bundles of striated crystals were observed by Genth and Penfield (Jacobson). They were up to 1.2 inches and were coated by alteration stains of copper, lead and zinc.

Brannerite - Tiny, black crystal found by Pete Modreski, mentions Jacobson. It was flattened, prismatic and lustrous.

Bromellite - According to Jacobson, the occurrence of bromellite by Larr in 1956 has not been confirmed and is unlikely.

Calcite - Jacobson reports it to be a very rare mineral in the Mt. Antero area. A weathered, 1cm rhombehedron was found by B. Loeffler in 2002 near the bottom of the snowpatch area.

Chrysocolla - Blue-green stains in some pegmatites, reports Jacobson.

Feldspar

Fluorite - Usually purple, green or white octahedrons; dodecahedrons are less common. Less than one inch octahedrons are the most common. They are usually associated with smoky quartz, albite, microcline, muscovite, phenakite and aquamarine. Jacobson mentions that the largest crystal to be found was an octahedron observed by Switzer that was almost 8 inches. A famous pocket of fluorites was found in 1982. It produced greenish, bubbly-faced, intergrown octahedrons.

Gadolinite - Very rare according to Jacobson, green gadolinite has been associated with garnet, triplite and blue beryl clots on the south knob.

Garnet - Trapezohedron crystals of spessartine up to 1/2 inch are reported in Jacobson.

Goethite after Pyrite - Cubes have been altered to goethite or may still have a limonite coating. Quite common as cubes, but Jacobson reports clusters of bladed crystals associated with feldspar, titanite, phenakite and bertrandite. B. Loeffler found two altered pyrite pyritohedrons on the south knob in 2002.

Helvite - An unconfirmed, yet possible, report by Larr mentions that the crystals "rarely exceed 1/2 inch in diameter and are easily confused with garnets." (Jacobson)

Hematite - Tiny brilliant crystals associated with phenakite, quartz, microcline and muscovite. Specular hematite has been found coating quartz and phenakite crystals. (Jacobson)

Ilmenorutile-strueverite - Flat, black, twinned crystals were observed by Montgomery in a pegmatite, reports Jacobson. Other pegmatites contained massive ilmenorutile.

Magnetite - Associated with biotite in pegmatites, reports Jacobson.

Microcline - Jacobson says it is "the dominant feldspar mineral present in the crystal cavities in the Mount Antero area." Up to 4 inches long and Baveno and Carlsbad twinning, according to Switzer (via Jacobson). Associated with smoky quartz, muscovite and albite.

Muscovite - Very common. Jacobson says that it occurs as clusters or rosettes up to 2 inches in diameter.

Orthoclase - The orthoclase in the Mt. Antero region is of the adularia variety. It is a common material in miarolitic cavities containing beryllium minerals. Associated with aquamarine, albite, bertrandite, fluorite, muscovite and phenakite. (Jacobson)

Phenakite - Antero is the top phenakite location in the U.S. and North America. Crystals can be white, clear or shades of yellow (amber being one of them) and are sometimes attached to quartz, thus many people confuse them with quartz. Jacobson shows sketches of several of the different habits found in the area. Many mineral associations exist.

Pyrite - Usually cubes that have been partially altered to limonite or fully altered to goethite.

Quartz - Clear to milky quartz crystals can be found in many locations on Mt. Antero. (Jacobson) Associated with fluorite, specular hematite and other minerals.

Schorl - An unconfirmed report by Pulfrey mentions tourmaline was found in pegmatites in the area. (Jacobson)

Smoky Quartz - The most abundant mineral in the Antero pegmatites, some crystals have been reported to weigh 50 pounds and up to 16 inches long. Some of them are gemmy; others are fractured and cloudy. Associated minerals include microcline, muscovite, albite, and fluorite, to name a few.

Spessartine - Trapezohedron crystals of spessartine up to 1/2 inch are reported in Jacobson.

Sulfur - Only one occurrence was reported in Jacobson. Yellow grains and a tiny sulfur crystal were found in a vug by Switzer and Montgomery. It is thought to be derived from the alteration of pyrite to limonite.

Titanite - Salmon-brown colored, double-terminated microcrystals were found in the clay filling of a miarolitic pocket by L. Piekenbrock. (Jacobson)

Topaz - Quite rare in the Antero pegmatites. Jacobson reports that it is only found in non-beryllium pockets. Mostly found in the south knob area, it is usually a sherry-brown color and gemmy in good crystals. Associated with microcline, smoky quartz, muscovite and fluorite. In fluorescent lighting, their color may fade.

Triplite - Occurs near the centers of blue beryl clots on the south knob.

Zircon - The cyrtolite variety of zircon. Brown-green microcrystals forming spherical masses on quartz and feldspar were found by L. and C. Piekenbrock, according to Jacobson. He also mentions radiating elongated crystals.

Other Notable Minerals
Tourmaline

Field Trip Reports

REPORT #1

REPORT #2

REPORT #3

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Digging on Mt. Antero in September of 2000.

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Hole dug into Mt. Antero where several smoky quartz crystals were found.

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The claim owner, Craig Cardwell (on the right), and part of his gang, Brian Busse and son on Mt. Antero. Brian does a lot of the digging with his sons while Craig is home in Texas.

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Surface collecting on the south knob of Mt. Antero.

References

  • M. Jacobson, 1993, Antero Aquamarines (ISBN 0-928693-07-4)
  • S. Voynick, 1995, Colorado Rockhounding (ISBN 0-87842-292-7)
  • J. R. Mitchell, 1997, Gem Trails of Colorado (ISBN 0-935182-91-8)
  • J. A. Murphy and P. J. Modreski, 2002, "Rocks & Minerals" (Vol. 77, July/August, pgs. 218-238)
Please see the reference(s) mentioned above for directions
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