A collector's guide to Piedmont Mine, USA: its geology, mining history and notable minerals, illustrated with the 24 specimens documented from this locality on EarthWonders.
Key facts
The Piedmont Mine of eastern Yavapai County, Arizona, is one of those localities whose importance is wholly out of proportion to its mining record. As an ore venture it was repeatedly promoted, renamed, evaluated, and re-evaluated, yet it produced almost nothing by Arizona mining standards. As a specimen locality, however, it became legendary through one small, enigmatic occurrence: malachite pseudomorphs after blocky azurite crystals, coated in drusy quartz or clear quartz points. The finest pieces show green, rhombic-to-blocky forms partially veiled in sparkling silica, set on dark hematitic breccia, pale quartz, or altered volcanic-looking matrix. In hand, a good Piedmont specimen has the curious optical tension that makes great pseudomorphs so compelling: the form says “azurite,” the color says “malachite,” and the surface flashes like quartz.
The deposit sits near Bloody Basin, north of Copper Creek and within sight of Brooklyn Peak, in high desert country of sparse grasses, prickly pear, juniper, and scrub. The local bedrock is described as massive, unfoliated granite cut by quartz dikes and by andesite-related structures; mineralization is treated in mine records as a fault- and shear-controlled, tabular vein system with near-surface oxidation. For collectors, the essential point is that the productive specimen environment was not a broad, specimen-rich copper mine like Bisbee or Morenci, but a narrowly localized oxidized vein-and-vug setting where azurite crystals were replaced by fibrous malachite and then mantled by quartz.
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Piedmont’s great specimens are famous not for abundance but for scarcity. The classic suite is generally described as numbering only about fifty pieces, with the best now dispersed into major Arizona private collections and institutional holdings. The date of the discovery is a point of collector lore: Barbara Muntyan’s later Mineralogical Record article and the 2022 Rocks & Minerals review give 1955, while her 2017 symposium abstract preserves a 1951 version of the story. Both accounts agree on the heart of the matter: a small group of Phoenix-area collectors, including members of the Thompson family and Monnie Speck, encountered a quartz-rich boulder or boulders at the mine and recovered the malachite-after-azurite specimens that made Piedmont famous.
Photo: Wikimedia Commons
That fame rests on a very specific look. The malachite is commonly fibrous and lustrous beneath the silica; in the best examples it forms compact, pseudo-rhombic crystals rather than simple green coatings. The quartz ranges from fine white sugar-like druse to transparent points, and the matrix may be dark red-brown to gray-black breccia, gray-white quartz, tan rock, or hematite-included material. Some pieces are not solid malachite forms at all but quartz casts where part of the malachite has been etched or lost, leaving a ghostly shell that records the former azurite crystal. That combination of replacement, coating, contrast, and scarcity gives Piedmont its place among Arizona’s classic pseudomorph localities.
Search for specimens: View all specimens from Piedmont Mine, USA
The Piedmont Mine is the Copper Creek–Bloody Basin Piedmont, not the separate West Congress/Congress-area Piedmont with which it has sometimes been confused in older database records and labels. The collector locality is in the Brooklyn Peak area of Yavapai County, Arizona, in the Tonto National Forest, near Bloody Basin Road, also known as Forest Service Road 269. Its mapped position is in the NW¼ of Section 33, T10N, R4E, on the Brooklyn Peak 7.5-minute quadrangle, with related claims reported to extend into nearby parts of Section 33 and adjoining townships and ranges. The corrected longitude places it near the mine workings west of Bloody Basin; older MRDS-derived data contained a one-degree longitude error that shifted a Piedmont record far to the west and helped foster locality confusion.
Geologically, Piedmont is a small Au-Ag-Cu vein occurrence rather than a large porphyry copper mine. Mine-database descriptions characterize the ore body as tabular, controlled by faulting, shearing, and igneous activity, with near-surface oxidation concentrating the copper minerals. Muntyan’s field description emphasizes medium-grained granite cut by subparallel quartz dikes trending roughly northwest to southeast, while database summaries note veins parallel to andesite dikes trending east-west to northeast and dipping at low angles. The working collector should read those descriptions together as a small, structurally controlled oxidized vein system in granitic country rock, locally interacting with quartz-rich and brecciated zones.
The old literature and prospectus claims give Piedmont a more dramatic mining history than the ground itself seems to justify. The original Copper Queen No. 1 through No. 6 claims were located in 1892 and were never patented. A later symposium summary refers to seven original claims, and the property ultimately carried a chain of names and promotions: Piedmont, Arizona Copper Queen, Legal Tender, Gold Flower, Copper Creek, and Bloody Basin Mineral Development Company property. One 1940s promotion tried to associate the “Arizona Copper Queen” name with Walter Douglas, son of Phelps Dodge president James Douglas, evidently to lend Bisbee-like prestige to a marginal property. Muntyan considered that connection highly unlikely.
The workings are similarly elusive. Promotional accounts described four shafts, originally to 300–350 feet, and one Piedmont shaft reportedly deepened to 1,050 feet with drifting on two levels. Later field checks found a much less convincing physical record: the collapsed Piedmont shaft, the collapsed Sunshine shaft to the southwest, little dump material, and a striking absence of the large dikes and waste piles one might expect if the promotional descriptions were accurate. Wayne Thompson and his uncle visited in 1981 and reportedly doubted whether much more than shallow prospect pits existed. The best sober summary is that the mine was a heavily promoted but poor producer; database records list production in 1936–1940, while Muntyan’s account says only one carload of ore was prepared for shipment during the long promotional life of the property.
The specimen-producing event is the true history. The celebrated malachite-after-azurite pseudomorphs were recovered from quartz-rich vug material at or near the mine by a small group of collectors connected with Phoenix’s Mineral Society of Arizona circle. The exact pocket—or pockets—has never been relocated. This matters because the surviving pieces do not all look alike. Their matrices vary from hematite-rich breccia to gray-white quartz crystals and tan, red-brown, or dark-gray rock; the quartz coating varies from opaque white druse to clear points; the underlying malachite ranges from forest green and emerald green to pale green and nearly white. That variation led Muntyan to infer that several vugs were probably involved, even though the popular story compresses the find into a single boulder and a single dramatic moment.
Collecting access today should be approached conservatively. The area lies in National Forest country, but old unpatented claims, modern claim status, access roads, seasonal closures, fire restrictions, and safety hazards can change. The collapsed Piedmont and Sunshine shafts are not collector attractions; they are unstable mine hazards. Any visit requires current land-status research through BLM Mineral & Land Records System data and appropriate National Forest guidance, and collectors should assume that anything beyond casual observation needs explicit permission where claims or private mineral rights are involved. From a specimen standpoint, the locality has been repeatedly searched without producing a second classic pocket, so field expectations should be modest: the Piedmont legend is built on old specimens, not on reliable modern productivity.
Piedmont malachite is at its best as a complete pseudomorph after azurite: compact, blocky to pseudo-rhombic crystals, commonly a few centimeters across and reported to about 5 cm in the classic find, replaced internally by fibrous, lustrous green malachite and then coated by drusy quartz. Ordinary material from the mine may be mere green coatings or crack fillings in quartz or feldspar, but the specimens collectors prize show unmistakable azurite morphology, with emerald to forest-green color visible beneath transparent quartz or glowing through a milky white silica crust. Smaller late finds include tiny blocky malachite-after-azurite crystals only 4–5 mm across west of the Piedmont shaft and south of Copper Creek, but the classic pieces are the larger pseudomorphs from the early-1950s/1955 Thompson-Speck find, especially those on contrasting dark hematitic breccia or flattened gray-white quartz crystals.
Quartz is both the gangue mineral and the visual signature of Piedmont. The mine area contains quartz dikes hundreds of feet long, but most are massive and not richly vuggy; collectible quartz occurs as crude vugs in boulders near the Piedmont shaft, as small sprays of centimeter-scale crystals, as gray-white flattened matrix crystals beneath pseudomorphs, and most importantly as the sparkling coating on malachite after azurite. The quartz overgrowth may be fine, opaque, and sugary white, or it may form clearer, larger points that leave the green malachite visible underneath. Piedmont quartz specimens without the copper-carbonate pseudomorph story are minor; the important pieces are those where quartz sharpens the contrast, protects the pseudomorph, or forms a partial cast after the malachite has been etched from the interior.
Azurite at Piedmont is most significant as the vanished parent of the famous pseudomorphs. The classic crystals are not preserved as fresh blue azurite from the Piedmont shaft area; they have been replaced by malachite, retaining compressed pseudo-rhombic forms up to several centimeters on edge. Actual azurite reported from the site is humble by comparison: sky-blue to medium-blue chalky blebs and coatings in rubble around the collapsed Sunshine shaft. For a Piedmont specimen, blue azurite is therefore not the normal target of connoisseurship; the desirable “azurite” is usually the readable former azurite habit, now green malachite and quartz-coated, with sharp blocky geometry and enough transparency in the quartz to let the replacement texture and color show.
Beyond malachite, quartz, and altered azurite, the documented Piedmont suite is small but more interesting than the mine’s economic record suggests. Barite occurs as tiny pale tan tabular crystals to only a few millimeters from a prospect pit north of Bloody Basin Road. Calcite and chrysocolla are known in old specimen material, including vuggy malachite-calcite and quartz-over-chrysocolla-over-malachite combinations. Hematite is important chiefly as included breccia and dark matrix contrast, not as large crystals. Jarosite is reported north of Bloody Basin Road with quartz and feldspar, and massive mottramite has been confirmed in small amounts along quartz dikes by Raman analysis. Native gold is carried in mine-database records for Piedmont-related Au-Ag-Cu mineralization, though it is not the collector identity of the locality. No type-locality mineral is documented from Piedmont; its rarities are historic, paragenetic, and aesthetic rather than taxonomic.
The first rule with Piedmont is provenance. The name “Piedmont Mine” has been applied to more than one Yavapai County mine, and older records have also muddied the locality by merging or misplacing West Congress/Congress-area Piedmont data with the Bloody Basin collector locality. A Piedmont pseudomorph should be labeled specifically as Piedmont Mine, Brooklyn Peak/Bloody Basin area, Yavapai County, Arizona, USA, ideally with a chain of ownership reaching one of the classic Arizona collections. Labels that say only “Piedmont Mine, Arizona” are not enough for a high-value piece.
The second concern is style. True classic Piedmont specimens are malachite after azurite coated by quartz, not simply green copper stain on quartz. The crystal forms should read as blocky or pseudo-rhombic azurite replacements, commonly with drusy quartz adhering to and wrapping the forms. Pieces with only malachite coatings, chrysocolla masses, or quartz veining may be genuine Piedmont material, but they do not belong in the same market category as the famous pseudomorphs. Conversely, many Arizona localities produce malachite-after-azurite, so an attractive green pseudomorph with no quartz coat and no old Piedmont provenance should not be upgraded on optimism alone.
I am not aware of a published suite of intentional Piedmont fakes, but the locality almost invites innocent mislabeling and over-interpretation. The small population of classic specimens, the variations among matrices, and the existence of quartz-coated copper minerals from other districts mean that provenance and morphology matter more than a casual visual match. The 2022 Rocks & Minerals review notes that some Piedmont pseudomorphs are partially hollow quartz casts where malachite has been etched or removed from within; such natural loss can be mistaken for damage, and damage can be excused too easily as “natural etching.” Examine broken edges, loose quartz druse, and repaired contacts carefully.
Condition is a major value driver. The quartz coating is hard, but the malachite beneath can be fibrous, thin, or partially absent, and the pseudomorphs may sit on brecciated matrix. Look for bruised quartz points, chipped blocky forms, missing corners, and areas where the green interior has been abraded. Old dynamite-related breakage is part of the locality lore, but it does not make a damaged specimen equal to an intact one. Strong pieces have complete, readable pseudomorphs, lively quartz sparkle, green color visible through or around the silica, and a matrix that frames rather than overwhelms the forms.
Rarity is real. The classic population is usually described as about fifty specimens, and many of the best are effectively locked in long-term private or museum collections. Piedmont pieces do appear on the market, but usually as old-collection dispersals or small specimens; larger plates and well-composed cabinet examples are exceptional. When one appears, the premium is for the full Piedmont story: malachite after azurite, quartz coating, old Arizona provenance, and an appearance that cannot be confused with ordinary malachite on quartz.
Piedmont is a story locality because the mine itself never quite lives up to its paperwork. The promoted mine was supposed to have substantial workings: four shafts, three or four hundred feet deep, and one shaft taken all the way to 1,050 feet with drifting on two levels. Then field people went to the ground and found the kind of evidence that makes geologists squint. The Piedmont shaft was collapsed at the collar. The Sunshine shaft, to the southwest, was collapsed too. Around them were not the enormous dumps one expects from deep underground work, but very little waste rock. Wayne Thompson and his uncle visited in 1981 and reportedly doubted that there were real shafts beyond shallow prospect pits. Barbara Muntyan and exploration geologist James McGlasson later found the same kind of unsettling absence: old claims, old stories, old promotion, but not the physical debris of a serious mine. Muntyan’s abstract preserves the perfect old mining aphorism for the place, attributed to Mark Twain: a mine is “a hole in the ground with a liar on top.”
The promotional history is almost theatrical. The claims began in 1892 as Copper Queen claims, a name already heavy with Arizona resonance because of Bisbee’s great Copper Queen. By the 1940s, one promoter went further, linking the Piedmont’s “Arizona Copper Queen” identity to Walter Douglas, son of James Douglas of Phelps Dodge fame. The implication was obvious: here was another Copper Queen, another possible Bisbee. Muntyan dismissed the connection as highly unlikely, writing that Walter Douglas probably did not know the property existed and, like his father, was too conservative to put his reputation behind what she called a “boondoogle.” The spelling is memorable, but the judgment is sharper than the typo: Piedmont’s glamour was being manufactured faster than ore.
Then there is the boulder. In the usual collector telling, Wayne Thompson, Sr., Evert Thompson, and Monnie Speck—Phoenix-area collectors connected with the Mineral Society of Arizona circle—reached the mine on what became the decisive trip. One version says they were on a picnic outing from Phoenix, a very long drive in the early 1950s, and found a huge vuggy quartz boulder. Another says Wayne, Sr. first found the boulder by himself beside the road, saw that a narrow crack was lined with pseudomorph specimens, and could not move or open the hard rock. He returned to Phoenix and recruited Evert Thompson, who had mining experience from the Black Hills of South Dakota and knew how to use dynamite, along with Monnie Speck, who ran a Phoenix rock shop with her husband. The story then becomes pure Arizona mineral folklore: dynamite, a split boulder, and roughly fifty specimens of malachite after azurite coated with quartz.
The best-known tragedy in the tale is the large plate. According to the version repeated in Muntyan’s abstract, the finest specimen was a plate about 30 cm, or 12 inches, long. None of the three collecting partners would surrender claim to it. Instead of remaining one of the great single Arizona pseudomorph specimens, it was broken into three pieces so each collector could take a share. Whether every detail happened exactly that way is hard to prove, but the story has the ring of collecting truth: desire, ownership, friendship, and the cruel arithmetic of a specimen that cannot belong to three people at once.
The pieces themselves argue with the simple version of the story. If all had come from one vug in one boulder, one might expect more uniformity. Instead, the surviving specimens vary dramatically. Some are on hematitic breccia, some on flattened gray-white quartz crystals, some on tan to red-brown or dark-gray matrix. Some carry fine white quartz druse, others clear points. The malachite ranges from deep forest green to emerald, grass green, pale green, and nearly white. Muntyan’s experienced conclusion was that the specimens probably came from several vugs and perhaps from more than one boulder. The legend prefers one explosive moment; the mineralogy quietly suggests a more complicated collecting campaign.
The old ownership trails read like an Arizona mineral roll call. Wayne Thompson, Sr. sold two fine examples early. One went to Ed Swoboda in the 1980s for his pseudomorph collection, then later passed through Jim Minette and into the Les and Paula Presmyk collection. Rukin Jelks bought another from Wayne, Sr. for the Arizona-Sonora Desert Museum when he was a trustee there. The museum later obtained much of Wayne Thompson’s material. Monnie Speck’s specimens went first to Sandi Aston of Phoenix, and that group was later acquired by Mark Hay, Dick Morris, and Keith Williams. Les Presmyk acquired many of Evert Thompson’s specimens through two purchases about a decade apart. For collectors, those names are not ornament; they are the authentication fabric of Piedmont.
The locality still keeps some secrets. The precise spot of the classic recovery has never been pinned down publicly, and repeated searches have failed to produce another comparable pocket. There are, however, odd related specimens: bright green vermiform chains of malachite pseudomorphs after an unknown material, quartz-coated and wormlike rather than blocky. Muntyan listed examples in the collections of Dick Morris, Les Presmyk, Paul Matt, Jim McGlasson, and herself. They are small footnotes beside the famous blocky pseudomorphs, but they reinforce the feeling that Piedmont’s oxidized vugs were stranger than its mining promoters ever understood.
