A collector's guide to Belshazzar Mine, USA: its geology, mining history and notable minerals, illustrated with the 32 specimens documented from this locality on EarthWonders.
Key facts
Belshazzar is one of the great specimen-gold localities of Idaho: a compact but unusually rich quartz-gold-bismuth lode on Fall Creek, west of Quartzburg in Boise County. Its fame rests on native gold in quartz—bright, saturated yellow, crystalline, and often wirelike or arborescent—but the mine is more than a pretty gold occurrence. It belongs to the Quartzburg district, at the southwest end of the Boise Basin “porphyry belt,” where Cretaceous granitic rocks of the Idaho batholith were fractured, intruded by Tertiary porphyry dikes, and mineralized by gold-bearing hydrothermal veins. In the Belshazzar lode, quartz, pyrite, arsenopyrite, galenobismutite and other bismuth minerals occur with free gold, making the deposit one of the classic American examples of gold intimately associated with bismuth sulfosalts.
The best Belshazzar specimens have a look all their own. Rather than bland blebs of gold in milky quartz, the finest pieces show brassy-yellow to rich lemon-yellow gold rising from quartz as ragged wires, branching crystalline ropes, leafy aggregates, and pseudo-wires made of elongated octahedral crystals. Under magnification, good pieces can show sharp octahedral, dodecahedral, cubic, tetrahexahedral, and trapezohedral faces packed into complex growths. Grey quartz, white quartz, arsenopyrite and dark metallic bismuth minerals give the gold contrast; the strongest specimens combine three qualities at once—visible crystallography, sculptural openness, and unambiguous natural attachment to the quartz lode.
Regional View
Country View
Historically, Belshazzar sits at the point where the Boise Basin story turns from placer romance to hard-rock geology. The first values came from disintegrated vein material on the divide between Fall and Canyon creeks, worked by placer methods in the 1870s. Later, tunnels, raises, tramways and mills followed the lode underground. The mine was already producing “fine specimens of free gold” from its upper levels in the early twentieth century; then, in the 1920s, it became one of the district’s important lode-gold producers. Much of the richest specimen gold from the active mining years appears to have gone to the assay office or the melting pot. That makes surviving historical pieces scarce, and it makes the later dump discoveries—especially the wire-gold finds made with metal detectors—exceptionally important to collectors.
Search for specimens: View all specimens from Belshazzar Mine, USA
The Belshazzar Mine is in the Quartzburg Mining District of Boise County, Idaho, on Fall Creek in sections 17 and 18, T. 7 N., R. 4 E., on the Harris Creek Summit 7.5-minute quadrangle. It lies west to southwest of Quartzburg, near the old Boise Basin lode-mining belt that includes the Gold Hill, Mountain Chief and Mayflower mines. Published coordinates place it at roughly 43.94° N, 116.01° W, with an elevation near 5,400 feet. Access historically followed roads from the Placerville–Quartzburg country; modern reports describe Forest Service Road 343B as steep, four-wheel-drive, rutted in places and partly overgrown.
Geologically, the mine is a gold-bearing fissure-vein system in the Idaho batholith, principally in Cretaceous biotite granodiorite and related quartz monzonitic rocks cut by porphyritic dikes. Belshazzar lies within the Quartzburg segment of the porphyry belt, where northeast- to east-trending vein fissures and shear zones interact with quartz monzonite porphyry, rhyolite porphyry, dacite or granophyric dikes, and lamprophyric dikes. The Belshazzar and Mountain Chief workings occupy opposite ends of a mineralized shear zone; the Belshazzar vein is the central and most developed structure. The Centennial vein lies nearby and was reached from Belshazzar workings by crosscutting, while a third, less-developed vein is also reported north of the main lode.
The ore is not a single simple quartz vein but a composite lode filling: sulfide seams and nests, older base-metal minerals, sheared and sericitized wall rock, and younger quartz lenses and seams carrying pyrite, arsenopyrite, bismuth minerals, dolomitic carbonate, stibnite locally, and free gold. The mineralization is classically pockety. Values were strongest in the quartz-rich ore, while wall-rock stringers were commonly poorer. Older reports emphasized that gold was most abundant in the upper and intermediate workings, especially above the No. 4 or 401 level; deeper workings still contained quartz, pyrite, arsenopyrite and bismuth minerals, but gold values diminished downward.
Development was substantial for a mountain lode mine. The upper workings began near the ridge where disintegrated vein material had first been placered. By the 1930s the mine had five principal tunnels and approximately 12,000 feet of workings. The three upper tunnels were each roughly 500 to 600 feet long; the important No. 401 level was about 1,700 feet long; and the No. 5 tunnel, driven near mill level roughly 400 vertical feet below the 401, was about 3,000 feet long. Raises connected the levels, and stoping was concentrated above the 401 and in intermediate levels below it. A tramway connected the hillside portals and ore bins to the mill on Fall Creek.
Mining began with surface and placer work in the 1870s after the disintegrated lode was recognized. The Belshazzar was located in 1875, and early placer-style working of the decomposed vein material reportedly yielded tens of thousands of dollars in gold. By 1884 high-grade ore was already present on the dump, and by 1905 the Belshazzar and Centennial property was attracting unusual attention in the district. A 10-stamp mill, moved from the Iowa mine, treated ore from the upper workings; free gold recovered well, but sulfide-rich third-level ore did not respond fully to amalgamation, prompting cyanide experiments and later milling improvements.
Corporate history passed through several phases. The Belshazzar Gold Mining Company was incorporated in 1906 and operated in a limited way through the first decade of the twentieth century, shipping bullion before its charter was forfeited in 1912. By 1915 the property was associated with George Tew, Lewis Klein and partners. The Idawa Gold Mining Company became the major later operator; state mining reports list Idawa as active in the 1920s and 1930s, with mine equipment, camp facilities, a 25-ton amalgamation and table-concentration mill, and eventually a well-developed underground system. Production peaked from 1926 to 1931. One USGS compilation gives shipped crude bullion from 1926 to April 5, 1931 as 28,680.59 ounces valued at $426,464.03, with concentrates adding $68,954.75 in gold and silver value. Later work was intermittent, and the last known production is reported in 1941.
Belshazzar’s specimen story is concentrated in a few levels and dumps. Quinn’s 1914 mining thesis noted “high grade specimen rock” from the No. 3 level drift. A 1927 report mentioned a “nugget” yielding $245 in gold—nearly 12 troy ounces at the gold price then in effect. In 1928, remarkably rich native-gold segregations were recorded between the 401 and No. 3 levels; hand-sorted lots reportedly contained dozens to hundreds of ounces of gold, and one specimen of nearly pure metal was said to weigh 105 ounces. Because such material had immediate bullion value, much of it was shipped or melted rather than preserved as mineral specimens.
Modern collecting history centers on the old dumps, especially waste near the 401-level portal. Metal-detector work in the 2000s brought Belshazzar back into the specimen market with hundreds of crystalline and wire-gold specimens, from microscopic wires to pieces containing many ounces of gold. These dump pieces are the source of many of the locality’s best-known modern specimens. The site is not a casual open collecting ground today: claim control, private or leased mineral interests, Forest Service land status, historic workings, environmental listings, and physical mine hazards all make permission and legal access essential.
Gold from Belshazzar is the locality’s defining collector mineral, occurring in and on quartz as bright yellow crystalline aggregates, arborescent growths, wires, pseudo-wires, ragged leaves, and compact high-grade masses associated with arsenopyrite, pyrite and bismuth minerals such as galenobismutite. Historical ore ranged from fine free gold in upper-level quartz to spectacular high-grade segregations between the No. 3 and 401 levels; modern specimens are best known from metal-detector finds on the old dumps, including pieces from tiny thumbnails to cabinet specimens with ounce-level gold content. Good Belshazzar gold is not merely heavy—it is textural. The desirable pieces show crisp or at least visibly crystalline surfaces, open branching or wirelike relief, attractive attachment to quartz, minimal bruising or flattening, and a natural contrast between the gold and grey-white quartz or dark metallic inclusions; ordinary pieces are more massive, crushed, acid-cleaned-looking, or lacking the sculptural crystallization that made the locality famous.
Quartz at Belshazzar is the essential stage on which the gold performs: white to translucent vein quartz, locally crystalline, sheeted parallel to vein walls, loose-textured and vuggy, with drusy cavities that can host fibrous galenobismutite needles, pyrite grains and free gold. In ore descriptions, younger quartz seams and lenses cut and envelop earlier sulfide-rich material, and the richest specimens tend to be quartzose rather than merely altered wall rock. As a collector mineral in its own right, Belshazzar quartz is rarely sought as standalone crystal specimens; its value is as matrix. The best quartz pieces are stable, clean enough to give strong color contrast, visibly part of the original vein rather than a broken lump, and ideally show vug texture, attached gold, arsenopyrite, galenobismutite or other metallic minerals that tie the specimen unmistakably to the mine’s bismuth-gold assemblage.
Other minerals recorded from Belshazzar include arsenopyrite, pyrite, galena, sphalerite, stibnite and galenobismutite, with bismuthinite and tetradymite also documented in the broader Belshazzar–Mountain Chief ore descriptions. No accepted mineral species is known to have Belshazzar as its type locality, but the mine is historically important for galenobismutite: a 1915 specimen from the Belzazzar/Belshazzar dump was studied by Earl V. Shannon at the United States National Museum and published in 1921 as a notable second definite occurrence of the species after Nordmark, Sweden. In Belshazzar ore, galenobismutite forms grey metallic grains, veins, elongated prisms and fibrous needles in quartz cavities, a subtle but highly significant companion to the gold for collectors who care about the full paragenesis rather than gold weight alone.
Belshazzar gold should be judged first as crystallized native gold and only second as bullion. The market naturally prices pieces by gold weight, but serious collectors pay the premium for crystallography, openness, matrix, provenance and locality style. A small, crisp, fully natural wire or arborescent group on quartz may be far more desirable than a heavier mashed mass. Under magnification, look for continuous natural attachment, original quartz contacts, consistent color and luster, and crystal faces that have not been rounded by aggressive cleaning.
No modern, locality-specific fake industry is well documented for Belshazzar, but the usual specimen-gold cautions apply with force. Gold glued into quartz, gold soldered or pressed onto a matrix, and placer gold mislabeled as lode gold are perennial risks in the specimen trade. Belshazzar pieces are especially tempting targets because the name now carries a premium. Strong provenance matters: labels tracing to recognized dealers, named collections, published specimens, or the well-known 2000s dump finds add confidence. The most convincing specimens show the Belshazzar look—crystalline gold in quartz with arsenopyrite and/or grey bismuth minerals—rather than generic rounded yellow metal.
The locality also has an unusual authenticity footnote from the mining era. In the 1931 Idawa Gold Mining Co. v. Cahill case, disputed high-grade ore was argued over in court; testimony included references to Belshazzar gold crystallized in arsenopyrite and to pieces allegedly treated with acid to change their appearance. That episode is not evidence that collector specimens today are routinely treated, but it is a reminder that Belshazzar ore has long been valuable enough to invite concealment, alteration and argument. Be cautious with pieces showing unnatural red staining, etched-looking quartz, or surfaces that seem chemically altered without good explanation.
Condition issues are typical of crystalline gold: wires and branches can be bent, flattened or broken; quartz matrix can be bruised; and old dump specimens may have small impact marks from blasting, milling, movement in waste piles, or recovery with digging tools. Gold itself is chemically durable, but the associated sulfides and sulfosalts are not all equally forgiving. Arsenopyrite and pyrite can tarnish, and fine sulfosalt needles may be fragile. Avoid ultrasonic cleaning on delicate matrix pieces, avoid acids unless a professional has a very specific reason, and do not over-handle high-relief wires.
Belshazzar specimens are available, but the supply is finite and uneven. Small thumbnails and wire fragments appear periodically; strong matrix thumbnails and miniatures are much scarcer; large cabinet pieces with open crystalline gold are major American gold specimens. Historical pieces from the active mining era are particularly desirable because so much early high-grade material was melted. Modern dump-find pieces, especially those from the 401-level dump and from known collections, form the core of today’s market.
In the old Boise Basin, placer miners found the first Belshazzar wealth not by driving neat tunnels into hard rock, but by washing decomposed vein material from the ridge between Fall and Canyon creeks. The lode had weathered into the kind of disintegrated, gold-bearing material that a placer miner could understand at once. Reports differ on the exact amount, but the surface work yielded roughly $60,000 to $65,000 in gold—an enormous sum for a body of broken vein material spread over about 30 acres. By 1884, about 200 tons of mostly high-grade ore sat on the dump, and the exposed vein was reported to be 15 feet wide. What later became a specimen-gold locality began as a half-hidden hard-rock source announcing itself through placer ground.
The mine’s richest years were not quiet. During the late 1920s, a section of the vein between the 401 and No. 3 levels produced extraordinarily rich native-gold material. Several hand-sorted lots contained between 48 and 435 ounces of gold, and one single reported mass of pure metal weighed 105 ounces. Some ore was so rich that it bypassed the mill entirely and went straight to the United States assay office in Boise. For a collector, that sentence has a melancholy edge: pieces that today would be centerpiece specimens were treated as bullion. The mine made money, but the mineral record lost untold specimens.
Then came the Cahill affair, one of the stranger courtroom stories in American specimen-gold lore. In July 1929, Archie L. Cahill was arrested at the Wilson Hotel in Salt Lake City. Officers seized sixteen pieces of high-grade gold-bearing quartz ore weighing 16½ pounds; one piece alone weighed 8 pounds. The Idawa Gold Mining Company claimed the ore had been stolen from the Belshazzar. Cahill denied it and spun a story involving Pat Flemming, an old prospector on Granite Creek, who supposedly had entrusted him with ore years earlier and later told him, “If I bump off, that pay streak is yours.” Cahill said there had been 37 quartz specimens and about 40 ounces of placer nuggets.
The opposing story read like a mining-camp detective novel. Ed N. Scott, an experienced miner and former sheriff, testified that Cahill had admitted finding a hidden “kidney” of high-grade ore while working night shift in the Belshazzar, covering it up, and taking thousands of dollars’ worth from the mine. The ore moved through farmhouses, pawn arrangements, hotel rooms, false names and planned sales. Cahill registered at the Wilson Hotel as P. J. Murphy; Scott used the name R. R. Emmerson. A large piece was nicknamed “Big Boy.” A map of the mine allegedly marked hidden caches, and when Scott later went underground he found the tamping stick where Cahill had indicated a cache would be.
The case even turned on mineral identification. A United States Assay Office worker compared the disputed ore with Belshazzar ore and found it of the same character and grade, noting large amounts of gold crystallized in arsenopyrite. A field geologist and mining engineer, Mr. Ballard, testified that typical Belshazzar ore could be recognized. Defense experts argued that ore could not be reliably identified by inspection. The appellate court ultimately sided with Idawa, finding that Cahill had secretly appropriated the ore while employed at the mine. For collectors, the episode is fascinating because it shows that Belshazzar’s high-grade gold-quartz-arsenopyrite ore was distinctive enough to become courtroom evidence.
Decades later, the old dumps produced a different kind of drama. The mine had not been commercially active since the 1930s, and for many collectors Belshazzar was obscure. In 2004, Idaho collector Allan Young went to the old dumps with a metal detector and found three very good gold specimens, later bringing the largest to the 2004 Denver Show. That discovery helped reintroduce Belshazzar to the specimen world. Subsequent metal-detector work, especially around the 401-level dump, yielded hundreds of wire-gold specimens. Some were tiny; others carried ounces of gold. The astonishing part is that these pieces had survived because they were thrown away as waste or missed by miners whose eyes were fixed on production, not cabinet aesthetics.
Earl V. Shannon, “On galenobismutite from a gold-quartz vein in Boise County, Idaho,” Journal of the Washington Academy of Sciences, 11(13), 298–300, 1921 — The key early mineralogical paper on Belshazzar galenobismutite, based on a specimen collected September 15, 1915 from the Belzazzar Mine dump and preserved in the United States National Museum.
A. L. Anderson, Geology and Ore Deposits of Boise Basin, Idaho, U.S. Geological Survey Bulletin 944-C, 1947 — The foundational geologic treatment of Boise Basin lode deposits, with detailed discussion of the Belshazzar mine’s workings, production, structure, and gold-bismuth-quartz ore.
C. P. Ross, “Some lode deposits in the northwestern part of the Boise Basin, Idaho,” U.S. Geological Survey Bulletin 846-D, 1934 — Important earlier USGS account of the Quartzburg-area lodes, including Belshazzar location, ownership, development and early twentieth-century production.
Victoria E. Mitchell, History of the Belshazzar and Mountain Chief Mines, Boise County, Idaho, Idaho Geological Survey Staff Report S-08-3, 2008 — The most focused modern institutional history of Belshazzar and Mountain Chief, with mine history, geology, maps and compiled production notes.
Matthew Vincent Quinn, Report on Bellshazar mining property, Missouri School of Mines and Metallurgy Professional Degree Thesis, 1914 — Early engineering thesis on the property, valuable for pre-Idawa conditions, workings, infrastructure and the note that high-grade specimen rock occurred on the No. 3 level.
Allan Young, “The Belshazzar mine, Boise County, Idaho,” The Mineralogical Record, 43(3), 325–336, 2012 — The principal collector-oriented article on the mine and its modern gold specimens.
Thomas P. Moore, “What’s New in Minerals—Denver Show 2008,” The Mineralogical Record, 40(1), 71–83, 2009 — Cited in locality records for modern Belshazzar native gold and quartz specimens seen in the mineral-show market.
Lanny R. Ream, Idaho Minerals, 2nd edition, L. R. Ream Publishing, 2004 — Cited in locality records for Belshazzar stibnite and broader Idaho mineral documentation.
Mindat: Belshazzar Mine, Quartzburg Mining District, Boise County, Idaho, USA — Concise locality page with coordinates, mineral list, references and photo links.
Western Mining History: Belshazzar Mine — Useful MRDS-derived summary of location, elevation, commodity and past-producer status.
Western Mining History: Boise County Idaho Gold Production — Clear district-level synthesis placing Belshazzar among the important Quartzburg producers and summarizing the porphyry-belt geology.
Western Mining History: Boise County Idaho Mining Districts — Helpful overview of the Quartzburg district, ore-shoot geometry, production style and gold-bismuth mineral assemblage.
Idaho Geological Survey: History of the Belshazzar and Mountain Chief Mines — Best single source for mine history, mapped workings and local geologic context.
Smithsonian Libraries and Archives: Shannon galenobismutite paper — Primary source for the United States National Museum study of galenobismutite from the Belshazzar dump.
Missouri S&T Scholars’ Mine: Quinn 1914 Belshazzar thesis — Early illustrated mining-engineering thesis with plates and a map of the underground workings.
Idaho State Archives: Belshazzar Mine records, MS 0352 — Archival guide to Idawa Gold Mining Company correspondence, operation reports and officer records from 1924–1935.
U.S. EPA Superfund Site Profile: USDA FS Boise NF: Belshazzar Mine — Official environmental site profile and location aliases for the Belshazzar mine area.
Nevada Canyon Gold: The Belshazzar Property — Current project summary with modern claim package, access notes, exploration overview and specimen-gold history.
Idawa Gold Mining Co. v. Cahill, 10th Circuit, 1931 — Court record of the high-grade Belshazzar ore dispute, valuable for its period details on specimen ore, provenance and ore identification.
Mineral Auctions: Belshazzar Gold, ex Madrid Collection — Archived specimen listing with useful collector description of Belshazzar gold crystallography.
Heritage Auctions: Native Gold, Belshazzar Mine, Kennedy Collection — Auction record for a large cabinet Belshazzar gold specimen, useful for market context and specimen description.
