Legrandite from the Ojuela Mine is the standard by which the species is judged: vivid lemon-yellow to orange-yellow sprays of glassy, elongated crystals, often rising from warm brown limonite like sparks from a gossan wall. The best pieces have a quality that is hard to fake visually: long, transparent to translucent blades or prisms in open, architectural bundles, bright enough to read as yellow even in modest light, and arranged with enough separation that the individual terminations can be appreciated.
Photo: Wikimedia Commons
The mineralogical setting explains the look. Ojuela is a deeply oxidized, zinc- and arsenic-bearing lead-silver replacement system in carbonate rocks, and its secondary mineral assemblage is one of the richest in the collecting world. Legrandite, Zn2(AsO4)(OH)·H2O, formed in oxidized zones where zinc from sphalerite-rich ore and arsenic from arsenopyrite-bearing assemblages were remobilized into late, open-space arsenates. The result is not merely “yellow arsenate on matrix,” but a suite of specimens that combine saturated color, contrasting limonite, and associated zinc arsenates such as adamite, paradamite, köttigite, and smithsonite.
Ojuela legrandite also carries historical weight. The species was originally described from the Flor de Peña Mine in Nuevo León, Mexico, in 1932, but the Ojuela Mine later produced the specimens that made legrandite a trophy mineral. Ojuela’s best legrandites are the material most collectors picture when the species is mentioned: freestanding, lustrous yellow crystal sprays, sometimes thumbnail-sized and delicate, sometimes large enough to anchor a serious cabinet display.
Collectors look first for color and form. A strong Ojuela specimen should be unapologetically yellow—lemon, canary, golden, or orange-yellow—with sharp, undissolved crystal faces, visible terminations, and a pleasing spray or bow-tie architecture. Matrix pieces are especially desirable when the legrandite stands proud from limonite, smithsonite, or pale arsenate crusts rather than being buried in clutter. Larger pieces with undamaged radiating clusters are far less common than small sprays, and old Romero-collection and classic 1970s-era pieces are especially prized when provenance is intact.
Search for specimens: View all legrandite specimens from Ojuela Mine, Mexico
The Ojuela Mine lies near Mapimí, Durango, on the northeast escarpment of the Sierra de Mapimí. It is not a single tidy hole so much as a large and complex mine group, with named entrances, stopes, levels, chimneys, and connected workings. The district’s mining history reaches back to the Spanish colonial period, and the broader Mapimí mining story is usually traced to the late sixteenth century. Mindat’s locality record lists the Ojuela deposit as first discovered in 1660; later historical summaries describe major industrial development in the nineteenth century, including conversion in 1893 into a major lead-silver property.
Geologically, Ojuela is a carbonate-hosted replacement deposit of the northern Mexican type. Mineralization was controlled by fractures and favored dolomitic horizons in limestone. Primary ore consisted largely of arsenopyrite, pyrite, sphalerite, and argentiferous galena, with calcite, quartz, fluorite, and limonite among the important gangue minerals. Oxidation of those sulfide bodies created Ojuela’s celebrated secondary mineral suite, particularly its arsenates. That oxidation, operating through large caves, pipes, vugs, and fracture-controlled ore zones, is what transformed a lead-silver mine into one of the great mineral-specimen localities of the world.
Legrandite is recorded from the area between the 13th and 17th levels, with the best pockets reported from the 17th level in 1979. The Ojuela occurrence is listed as world-class for the species, with elongated prisms reported to 28 cm. Even allowing for the distinction between individual crystal length and displayable specimen aesthetics, that figure conveys why Ojuela dominates the collector imagination for legrandite: no other locality has supplied comparable numbers of showy yellow specimens with this combination of size, brilliance, and form.
The mine’s specimen history is inseparable from a few key episodes. W. F. Foshag of the Smithsonian visited in 1927, bringing mineralogical attention to a district that had already been mined for centuries. Significant collector production came later, especially after Dan Mayers and Francis Wise encountered a major adamite grotto in 1946. Legrandite’s own great collector-production years include the late 1970s, with 1979 singled out in locality records for the best pockets. Ojuela has continued to yield specimens sporadically through small-scale mining and specimen recovery, though the era of abundant classic material is long past.
Access today is not comparable to casual public collecting at a dump. Ojuela is a historic mine and tourist destination, reached through the celebrated suspension bridge area near Mapimí, and guided mine visits are part of the modern site experience. Serious mineral specimens come through local miners, cooperative or small-scale operations, and established dealer channels. Collectors should treat Ojuela labels with respect but also with caution: the mine is so famous that its name has been attached to material from other Mexican localities, especially for species such as mimetite, smithsonite, pyromorphite, and so-called endlichite.
Ojuela legrandite is most admired as radiating sprays, bow-tie groups, divergent sheaves, and upright clusters of elongated monoclinic prisms. Individual crystals are commonly slender, bladed, or acicular-prismatic, with chisel-like to wedge-like terminations. The finest specimens show discrete crystals with enough air between them that the spray reads three-dimensionally rather than as a compact yellow crust.
Color ranges from pale yellow through bright lemon-yellow to rich orange-yellow. The best collector pieces are saturated lemon to canary yellow with strong translucency, and many have a warm internal glow when backlit. Luster is typically vitreous to slightly resinous. On the finest examples the crystals are not merely yellow; they are transparent enough to show internal brightness and sharp enough to display crisp terminations.
Typical collector specimens range from tiny sprays of a few millimeters to thumbnails and miniatures with crystals around 5 mm to several centimeters. Fine miniatures with isolated sprays are strongly collected. Cabinet specimens with large, undamaged, radiating groups are much rarer. Published and database records note elongated prisms to 28 cm from Ojuela, but most display-quality pieces on the market are far smaller; the best pieces are judged not just by maximum dimension, but by crystal separation, color, luster, and lack of bruising.
The classic matrix is limonite or goethitic gossan, usually brown to rusty orange, providing ideal contrast for yellow legrandite. Associated minerals include adamite, paradamite, smithsonite, köttigite, goethite, parasymplesite, hydrozincite, calcite, mimetite, gypsum, ojuelaite, and mottramite. Adamite and paradamite associations are especially important because they place the specimen squarely within Ojuela’s famous zinc arsenate paragenesis. Smithsonite and limonite matrix pieces can be particularly handsome when the legrandite is perched cleanly in a vug.
Quality is determined by five factors: color, isolation, crystal size, condition, and provenance. A small, brilliant, undamaged spray on matrix can be more desirable than a larger but dull or crowded cluster. Top examples have lemon-yellow color, glassy faces, sharp terminations, little to no contact damage, and attractive placement. Provenance to older Mexican collections, the Romero collection, or long-established dealer stock can materially improve collector confidence and desirability.
Legrandite is fragile in the practical, collector sense. Its elongated crystals are easily chipped, bruised, or snapped at the tips, and radiating clusters often have tight internal contacts where damage is hard to see in photographs. When evaluating an Ojuela specimen, inspect terminations, the outer edge of sprays, and points where crystals emerge from matrix. A few small contacts on older pieces are common and may be acceptable, but broken main crystals on the display face strongly affect value.
The most common condition issues are missing terminations, rubbed crystal edges, limonite dust caught between crystals, old repairs, and incomplete sprays where a central fan has lost its outer needles. Because legrandite’s yellow color is so visually dominant, subtle bruises can be overlooked at first glance. Magnification and angled lighting are essential, especially for higher-value pieces.
No widely documented, recurring treatment problem appears to be specific to Ojuela legrandite itself in the way that artificially colored blue hemimorphite is documented from Ojuela material. Still, the broader Ojuela market has known authenticity problems. Some specimens sold as Ojuela are actually from other Mexican localities, and certain Ojuela-attributed materials—especially artificial kobyashevite and artificially colored electric-blue hemimorphite—have been specifically called out in locality references. That context matters: a legrandite label should be judged by mineralogy, matrix, habit, dealer reputation, and provenance, not by locality name alone.
Genuine Ojuela legrandite has a distinctive look, but labels should still be scrutinized. Ojuela matrix is commonly brown limonitic gossan, often with zinc arsenates or smithsonite, and the legrandite habit tends toward bright yellow sprays and elongated prisms. Tsumeb and Sterling Hill legrandites are mineralogically legitimate but visually and paragenetically different; they should not be confused with Ojuela material. Conversely, a yellow arsenate spray from Ojuela should not be assumed to be legrandite without morphology or analytical support, because the mine contains many arsenates and related secondary minerals.
Rarity is tiered. Small Ojuela legrandite specimens appear regularly enough that patient collectors can obtain representative examples. Fine, undamaged, well-composed miniatures are much less common. Large, old, brilliant, matrix specimens with strong provenance are genuinely scarce and often move quickly when offered. The best pieces are no longer “available” in any casual sense; they reside in established collections and surface mainly through collection dispersals or specialist dealers.
Current market availability is uneven. Dealer platforms and auction archives show periodic Ojuela legrandite offerings from small thumbnails to multi-thousand-dollar miniatures and small cabinets. Price rises steeply with color saturation, crystal size, isolation, and damage-free display. A modest but honest thumbnail may be affordable compared with many world-class species, while a top Romero-style or classic 1970s cabinet piece belongs in the serious Mexican-minerals market.
The Ojuela story begins as an ore story long before it becomes a specimen story. The mine was worked for rich secondary silver ores from shallow levels, then transformed in the late nineteenth century into a major lead-silver property. By the time early mineralogical notes described it, Ojuela was already large enough that one could spend weeks underground without returning to the same place. That scale is crucial to understanding why the mine produced so many different collector minerals: not one pocket, not one vein, but an immense oxidized system of caves, pipes, stopes, and levels.
The bridge is part of the mineral story because it shaped the way people encountered the mine. The Ojuela suspension bridge spans the canyon at the old mining site, connecting the ghost-town side to the mine workings. Historical summaries credit the bridge to Wilhelm Hildenbrand and the John A. Roebling’s Sons Company, the firm associated with major suspension-bridge engineering. Its main span is recorded at 271.5 meters, with 315.5 meters between pylons. Today visitors cross it on foot, but for the collector the bridge is more than a tourist image: it is the threshold between the desert light of Mapimí and the underground world that yielded adamite, paradamite, köttigite, and the yellow legrandite sprays that made the mine famous.
The collector era sharpened in 1927, when W. F. Foshag of the Smithsonian visited Ojuela. The mine had already been producing ore for centuries, but mineralogists and collectors had not yet absorbed what its oxidized zones could mean. The decisive postwar specimen moment came in 1946, when Dan Mayers and Francis Wise discovered a huge adamite grotto. That episode is usually told as an adamite story, but it marks the broader change in Ojuela’s identity: from an old lead-silver mine to Mexico’s greatest specimen locality.
Legrandite’s own legend turns on the lower levels. Locality records place the mineral between the 13th and 17th levels, and they single out 1979 on the 17th level for the best pockets. This is the kind of line that serious collectors read twice. In an oxidized mine where the difference between ordinary brown gossan and a world-class specimen pocket may be one narrow vug, the level number matters. A 17th-level Ojuela legrandite is not just “from Mexico”; it is from the part of the mine that produced the species at its most ambitious scale.
The Romero collection adds the human dimension. One photographed Ojuela legrandite from that collection is a 6 × 3.8 × 3 cm small cabinet piece: a radiating cluster with crystals to nearly 4 cm, perched on limonite matrix, described as pure lemon yellow and with only trivial contacts at the base. The file history notes that the Romero collection contained what was described as the single most important stash of fine legrandites still together in one place. That specimen reportedly stood as a core display piece in Romero’s museum and later spent about a decade on loan to the University of Arizona Mineral Museum. For collectors, that is the path a great legrandite can take: pocket, miner, dealer or collector, private museum, university display, then back into the literature and market memory.
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