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Stonetree Opal Mine (WRT Stonetree claim; BLM-NMC No. 865655), WRT Stonetree group ("Dominion Opal Mine"), Virgin Valley District, Virgin Valley, Humboldt Co., Nevada, USA

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Latitude & Longitude (WGS84): 41° 51' 39'' North , 119° 2' 37'' West
Latitude & Longitude (decimal): 41.86083,-119.04361
Köppen climate type:Dsb : Warm, dry-summer continental climate

The Stonetree deposit was one of the earliest mining claim locations in the Virgin Valley Mining District. Although known to exist much earlier in time, it was first "officially" reported by D.B. Sterrett in 1913 as being owned by "several parties". At one time the mine was owned by renowned Flora H. Loughhead ("Lockheed") Gutierrez, and was referred to in 1916-1918 as the "Giant Tree" Opal Claim, and was sold by Gutierrez to the Rainbow Ridge Mining Company in 1918. Between 1918 to 1940, the surface float and alluvial (placer) deposits of opal were exhausted and the claim subsequently became idle and abandoned. It was relocated as a placer deposit in 1966. In 2004 it was located as a lode (in-place) deposit when it became a part of the ten-claim WRT Stonetree claim group by the Wentzell Revocable Trust. Annual Assessment work and development by agents of The Wentzell Revocable Trust from 2007 to present uncovered large amounts of precious black, crystal, jelly and other opal types, including a large harlequin black opal. The claim obtained its name from the large 30+ foot petrified tree on the property. Mining efforts are undertaken in such a way to protect this landmark fossil for future generations of the public to enjoy.

The Stonetree deposit is similar to all of the other precious-opal bearing deposits in Virgin Valley. The mining claims are underlain by in-place, horizontal ash, tuff, and tuffaceous sandstone beds. The opal-bearing horizon can be traced and followed and averages more than 4 feet (1.2 m) thick and consists primarily of light-colored bentonite containing varying amounts of petrified wood, rhyolite pebbles, ash, and opal. Precious opals are usually found in the upper half of the horizon. The opal-bearing layer is continuous and in-place. The precious opals which are mined from this deposit are as bright as, if not brighter than, opals from the other area mines. The largest precious opal found on this group of claims was approximately four (4) pounds. Petrified wood is not mined on any of the claims but the precious opal is found in association with petrified wood.

The WRT Stonetree Group of lode mining claims includes, in addition to the WRT Stonetree Claim, the WRT Moonbeam's Child, WRT Pleasures, WRT Black Beauty, WRT Fireworks, WRT Cloud Nine, WRT Fiery Embers, WRT Fiddles & Diddles Opal, WRT Sacred Fire, and WRT Virgin Desert Flame. The claim group is approximately 206.6 acres, of which at least 183+ acres contains opal-bearing deposits and reserves. The 10 lode claims making up the group were sold by the Wentzell Revocable Trust to Alvin W. Wentzell Jr., in 2011 and 2012. Dominion Opal Mines & Exploration is currently (2012) in charge of mining and assessment work operations through its agents. Officially known as the WRT Stonetree claim, BLM-NMC#865655 (individual claim serial numbers NMC#865653 thru NMC#865662).

Mineral List

1 valid mineral.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

Pliocene - Miocene
2.588 - 23.03 Ma

ID: 2775925
Younger tuffaceous sedimentary rocks

Age: Neogene (2.588 - 23.03 Ma)

Stratigraphic Name: Horse Camp Formation; Esmeralda Formation; Belted Range Tuff; Timber Mountain Tuff; Paintbrush Tuff; Crater Flat Tuff; Muddy Creek Formation; Siebert Tuff

Description: Tuffaceous and other young Tertiary sedimentary rocks. Most of these rocks are sedimentary with a strong volcanic component - a few are tuffaceous with a strong sedimentary component. This unit includes rocks originally mapped as the High Rock sequence in Washoe County; the Horse Camp Formation in northern Nye County; the Esmeralda Formation in Mineral and Esmeralda Counties; older lake beds in Lincoln County; the Belted Range Tuff; the Indian Trail Formation (now abandoned); Timber Mountain, Paintbrush, and Crater Flat Tuffs; Wahmonie and Salyer Formations in southern Nye County; the Siebert Tuff in Esmeralda County; the Muddy Creek Formation in Clark County; and the Thousand Creek and Virgin Valley “beds” in Humboldt County; and other unnamed units. It corresponds to units Ts3 and Tts from the 1978 State map. It is present in all counties.

Lithology: Major:{sedimentary,volcanic}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


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Sterrett, D.B. (1914) Gems and Precious Stones chapter in United States Geological Survey Mineral Resources U.S., for 1913. Pages 677-680, at 677.
Sinkankas, John (1959) Gemstones of North America. (D. Van Nostrand Company, Princeton, N.J.). Figure 30 at page 116.
Butler, Gail (1987)(Sept.) Opal in Virgin Valley. Rock & Gem Magazine, p. 36-38.
Castor, Stephen B. (2005) The Nevada Mineral Industry 2004. Nevada Bureau of Mines and Geology Special Publication MI-2004, University of Nevada, Reno. At page 53 under "Gemstones."
United States Geological Survey (USGS) Minerals Yearbook, 2004, Volume 2, Area Reports, Domestic; at page 30.4 under "Gemstones."
Mining Claim Files for NMC865653 through NMC865662 (WRT Pleasures & Stonetree Group claims). U.S. Department of the Interior, Bureau of Land Management, Nevada State Office, Reno, Nevada USA.
Historical documents pertaining to the Virgin Valley Mining District in the possession of Christopher Wentzell & The Wentzell Revocable Trust.
***add other references***

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