Bancroft, Peter (1984) Gem and Crystal Treasures. (Western Enterprises, Fallbrook CA, with the Mineralogical Record, Tucson AZ). Virgin Valley featured on pages 83-85.
Butler, Gail (Sept. 1987) Opal in Virgin Valley. Rock & Gem Magazine, p. 36-38.
Castor, Stephen B., & Ferdock, Gregory C. (2004) Minerals of Nevada. Nevada Bureau of Mines & Geology Special Publication 31, UNR Press (Reno, NV); Virgin Valley at pages 75-76, 349-350.
Castor, Stephen B. (2005) The Nevada Mineral Industry 2004. Nevada Bureau of Mines & Geology, Special Publication MI-2004, University of Nevada, Reno; (Wentzell Virgin Valley claims at page 53 under "Gemstones"). Click HERE FOR LINK to Google Books.
Downing, Paul B. (2003) Opal Identification and Value (Revised). Majestic Press, Estes Park, CO.
Downing, Paul B. (2003a) "Dig Your Own Opal," Rock & Gem Magazine, October, p. 12, 14.
Dufurrrena, Carolyn (1986) "Romancing The Stones: Virgin Valley's Opal Barons invite fellow gem hunters and history buffs to dig in and share the wealth." Nevada Magazine, (May/June 1986 ed). To read the article online, CLICK HERE FOR LINK.
Eckert, Allan W. (1993) "Opal-Logue." Lapidary Journal Magazine, Vol. 47, #3, p. 36-40.
Eckert, Allan W. (1997) The World of Opals. John Wiley & Sons (New York). A small preview of this text is viewable on GoogleBooks: CLICK LINK HERE.
Eyles, W.C. (1964) The Book of Opals. Charles E. Tuttle (Rutland, VT).
Jones, B. (2004) Precious Opal. Rock & Gem Magazine, October, p. 12-14.
Mining Claim Files for NMC#865653 thru NMC#865662 (WRT Pleasures & Stonetree Lode Group claims). U.S. Dept. of the Interior, Bureau of Land Management, Nevada State Office, Reno, Nevada USA.
Papke, K., & David, D. (2002) Mining Claim Procedures for Nevada Prospectors and Miners. Special Publication 6. 5th Edition. Nevada Bureau of Mines & Geology, Mackay School of Mines, University of Nevada, Reno. CLICK HERE FOR LINK.
Sinkankas, John (1959) Gemstones of North America. (D. Van Nostrand Company, Princeton NJ). Figure 30 at page 116; Virgin Valley at pages XXX-XXX.
Sinkankas, John (1997) Gemstones of North America, Vol. #3. Geoscience Press (Tucson, AZ).
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.
U.S.G.S. (1984) Mineral Resources of the Charles Sheldon Wilderness Study Area, Humboldt and Washoe Counties, Nevada (...) United States Geological Survey Bulletin #1538. U.S. Government Printing Office, Washington Dc, and USGS. (Often referred to as the "Cathrall et al Report."). Geological_Survey_Bulletin.pdf
Turley, Dick (1987) A Summer of Fire. Rock & Gem Magazine, (July), p. 48-50.
Zeitner, June C. (1986) Precious Opal in the United States. Lapidary Journal Magazine, Vol 40 #3, p. 42-48.
United States Geological Survey (USGS) Minerals Yearbook 2004, Volume 2. Area Reports, Domestic, at page 30.4 under "Gemstones." CLICK LINK HERE.
To read about Nevada's great minerals, I would highly recommend obtaining a copy of the NEVADA monograph by Lithographie LLC (2013) which includes a chapter on Nevada Turquoise and Opal. Click on the image of the book below to go to the Lithographie Website. This is a must have for any connoisseur of fine Nevada minerals:
The Virgin Valley area contains a barely scratched precious opal reserve and resource, and is part of a 68,000 acre area set aside for entry under the general mining laws. The opal-bearing areas are spread out over a large area, but the precious opal occurrences are smaller isolated deposits within the region. Common opal is just that, "common," and can be found throughout the area, along with petrified wood, agate, and obsidian. Most precious opal producing ground is covered by valid mining claims. Very few of the nearly 200 claims in the Valley actually produce precious opal. There are five patented mine groups in the mining district. Virgin Valley is considered to be the premiere source of precious opal in the United States (Jones, 2004, p.14). The most productive mines to date have been the famous Royal Peacock, Virgin Opal (Bonanza), and Rainbow Ridge Mines (USGS, 1984, p.6). Virgin Valley is located in the isolated extreme northwestern corner of the State of Nevada in Humboldt County, within the Sheldon National Wildlife Refuge. The closest town is Denio (NV) about 32 miles to the northeast (paved road). Lakeview (OR) is 95 miles northwest (paved road), and Winnemucca (NV) is about 120 miles southeast (paved road). Virgin Valley can also be accessed from Cedarville (CA), 56 miles away, during summer months by gravel road (not recommended unless experienced with this area). The closest gas is available in Fields, Oregon (See LINKS, BELOW). The average high desert mining season is from May until November, but the area is sometimes accessible year-round, weather permitting.
Virgin Valley precious opals are considered to be the brightest and most colorful opals in the world, and on many occasions, have been found in remarkably large pieces. The world's record-size precious opal weighed 130 pounds and was found in the Northern Lights Mine (fee dig) of the Royal Peacock Mine group in Virgin Valley. However, Virgin Valley opals have also gained the notorious reputation for cracking or crazing and being unstable for gems. It is true that the majority of opal found in Virgin Valley is not suitable for cutting or polishing. Rough stones are best placed in liquid-filled display domes which make breathtaking display specimens. Nothing can compare to a precious crystal black opal specimen from Virgin Valley, but few stand up to the test of time as gemstones. Some area miners will sell treated opals, ie., treated with "Opticon," "Opal Cure," or other plastic polymer fracture fillers which attempt to hide the cracks or crazing in the opal. These "treated" stones have been enhanced to hide the cracks and flaws in the stone, and this should be disclosed, and correspondingly, priced far below what a natural uncrazed opal from a reputable field in Australia would cost. This is not to say that Australian opals don't crack, as a good percent does; however, the Virgin Valley field is known for producing more unstable opal than probably any other field in the world. As specimens in glass filled domes, there are no comparisons to the color and "fire" of Virgin Valley Opal. The statements as to instability and treatment also goes for the "Conk" opal. Most conk opal is a light brown color, and is very soft. It has a tendency to split or crack along the opal pores, and to pit when polished. Treating the wood with polymers holds the stone together and darkens the material which makes the opal stand out brighter. These stones should also be disclosed as treated, and priced accordingly, far below what a natural solid Boulder opal would be priced. Put very simply, that is why you will see many of these types of opals sit in the local shops or dealer displays for years, and decades, without being sold. People know they are unstable and do not want to pay the unreasonably high asking prices for them. I would say that the vast majority of opal from Virgin Valley should be classified as specimen material, although stones have survived as gems (but the question is for how long). One example is the famous Robeling Black Opal from the Rainbow Ridge Mine in Virgin Valley. It was discovered in 1917 and remained stable for many years, and then began to crack and craze while on display in the Smithsonian in the 1940's or 1950's. Now the stone's surface is covered with these fractures. It is still a beautiful specimen.
Despite the fact that most of the opal from Virgin Valley is plagued with the demonstrated instability, many diggers have been coming to Virgin Valley for years and even decades to dig the beautiful opal found within the hard clay zones and deposits there. Rarely, promising claims are offered for sale and proven claims are "quickly snapped up by a hopeful digger" (Turley, 1987, p. 50). Many claim owners do not even work their claims, or only do so on a hobby basis, or hold onto the deposits as an investment while only performing the minimally required annual labor. There is much potential for the Virgin Valley deposits as has been demonstrated by several producing mines that have been operated successfully for years and even decades. Fee-digging operations bring in the majority of local business, followed by the sale of "gem" and specimen material locally and at gem and mineral shows. Everyone is always interested in digging in a "new" productive mine which is opened to the public. In recent years, several other well-known claims and producing mines in Virgin Valley (the Royal Peacock and Bonanza Opal Mines) have been featured on the Travel Channel's "Cash & Treasures" TV program.
LINKS OF INTEREST:
ROYAL PEACOCK OPAL MINE, VIRGIN VALLEY. The best fee dig in the Valley. Highly recommended. Both undisturbed bank and tailings digging. Campground and store. The world's largest precious opal log was found at the fee dig mine here in the 1990's. I would recommend digging for at least 2 or 3 days or longer. The more time you have to dig, the better your chances at finding an opal, although "first timers" have found beautiful opals in one day. You can learn alot from the other experienced opal diggers staying at the camground.
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Alvin W. Wentzell Jr., sole owner, Dominion Opal Mines.