Red River Floodway, Manitoba: gypsum rosettes (selenite) from glacial Lake Agassiz clays; amber blades, gem-like transparency, and limited pockets.
Key facts
The Red River Floodway at Winnipeg, Manitoba, is one of the rare collector localities created not by a mine, quarry, or natural outcrop, but by a major civil-engineering cut through a glacial clay plain. The specimens that made it famous are gypsum rosettes—generally sold and labelled as selenite—formed as secondary CaSO4·2H2O crystals in thick Pleistocene Lake Agassiz clays. The floodway is important because its deep, long banks exposed horizons that ordinary prairie topography almost never reveals: compact balls of intergrown gypsum blades, commonly amber to honey-yellow, from which larger transparent twinned crystals project like wings, fins, or the now-familiar “duckbill” forms. Good Red River pieces are true floaters, sculptural on every side, with no hard matrix and with the clay carefully washed away; the best are lustrous, gemmy, well balanced, and bright enough under ultraviolet light to be memorable even to collectors who do not specialize in fluorescent minerals.
Regional View
Country View
The locality’s collector significance is inseparable from the floodway itself. Built east of Winnipeg to divert Red River floodwater around the city, the channel cut into a flat clay plain deposited by glacial Lake Agassiz. During construction, and later during controlled collecting and expansion-related work, collectors encountered gypsum clusters in discrete pods rather than as a continuous, easily followed bed. That poddy distribution, combined with restricted access to the floodway, is why attractive Red River selenites have always had a “find” quality: even in a productive zone, much digging can produce little, and a pocket that yields good rosettes may abruptly fade.
Photo: Rob Lavinsky, iRocks.com / Wikimedia Commons
The classic specimen is a rounded rosette of smaller, interlocked blades with one or more larger, clearer crystals emerging from the core. Some are pale yellow or nearly colourless; many of the most coveted examples show a warm sherry-to-amber colour. Collectors prize undamaged projecting crystals, sharp twin outlines, glassy lustre, and the curious combination of fragility and brilliance: a Red River selenite may look robust in a photograph, but in hand it is soft, cleavable, and easily bruised.
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The Red River Floodway locality lies in and near Winnipeg, Winnipeg Metro Region, Manitoba, Canada. It is a collector occurrence of secondary gypsum in glaciolacustrine clay, not an ore mine in the metallic sense. The “deposit” is a series of gypsum-bearing horizons and pods within Lake Agassiz clay, exposed where the floodway and associated excavations cut deeply enough below the prairie surface. The channel is approximately 49 kilometres long in collector literature, and the original floodway was constructed in the 1960s as flood-control infrastructure; its purpose was never mineral production, but its excavation revealed one of Canada’s most distinctive gypsum occurrences.
Geologically, the host is fine-grained clay laid down in the basin of glacial Lake Agassiz, the enormous Pleistocene lake that covered much of southern Manitoba and adjacent parts of the northern United States after the last ice age. The clay plain is generally subdued, poorly exposed terrain, so deep artificial cuts are especially important. The gypsum occurs as rosettes and crystal clusters in clay rather than in bedrock veins or evaporite quarry walls. The chemistry appears to reflect calcium and sulphate moving through shallow groundwater in clay-rich sediments; Manitoba geological work discusses carbonate-bearing clays as a calcium source and sulphate derived from oxidized organic sulphur in the clay, with fractures and old water-table positions helping localize growth. This slow, clay-hosted setting explains why the best crystals are clean floaters with no hard matrix, and why the crystals may preserve subtle zoning, inclusions of clay, and differences in habit from one depth to another.
There are no conventional ore bodies here. Productive zones are collector “pods” of concentrated rosettes. Reports from experienced collectors describe the rosettes as unevenly distributed along the floodway banks, with horizontal banding of habits inside some pods. Shallower material tends to form compact amber balls of small intergrown blades, sometimes with larger transparent amber blades protruding from the core. Deeper material has been described as larger, more distinct, blockier, and commonly yellow to colourless. Some large blades include clay or small rock fragments, and crystals close to the surface are often damaged by frost or dissolution. The fact that gypsum references in drillholes do not automatically predict commercial-quality rosettes is important: the mineral can be present without forming collectable, well-developed specimens.
The collecting history began with the floodway works themselves. Selenite crystals were reported in the Winnipeg region from the time floodway work began, and during construction significant numbers were unearthed. Rockhounds collected them for decades afterward, and by the 1990s the locality was firmly established in Canadian collecting literature. Commercial exploitation took place in limited zones, including two large pits excavated in 1997 and 1998 along the floodway banks near the Trans-Canada Highway by AMA Mines and associates. Mindat also records the Block and Blady Open Pit as a sublocality of the Red River Floodway. University of Manitoba geoscience staff and students used those pits for field and laboratory study of rosette morphology, zoning, host-clay mineralogy, chemistry, and geophysical response.
Collecting access today is not casual. The floodway is critical flood-control infrastructure, and parts of the channel and adjacent lands are restricted for safety and operational reasons. Public collecting without permission is not appropriate. Documented modern collecting has taken place under special permission, notably organized digs involving the Mineral Society of Manitoba, with limited time windows, membership restrictions, safety requirements, and backfilling or restoration of disturbed ground. Fine specimens on the market therefore tend to come from older construction-era collecting, organized club digs, expansion work, or limited controlled excavations, rather than from open public access.
The notable finds are not named pockets in the style of a hard-rock mine, but productive clay pods. The Trans-Canada Highway area, including zones near rail infrastructure, is repeatedly mentioned in collector accounts. Rich pods there produced classic floaters: rounded selenite “balls” with projecting amber twins. Field accounts describe pits several metres deep, wire-probing of clay to locate hidden crystals, and the delicate removal of clay jackets around specimens before careful washing. Finds of 6 cm pieces have been reported during modern organized digs, while collectors hoped for specimens up to roughly 14 cm across; geological literature notes rosettes occasionally exceeding 10 cm in diameter, and dealer and museum specimens show cabinet-quality floaters in the 5–9 cm range.
At the Red River Floodway, gypsum is the mineral species and the whole story: CaSO4·2H2O crystallized in Lake Agassiz clay as rosettes, balls, starbursts, and twinned blades rather than as massive evaporite or ordinary vein gypsum. The characteristic pieces are clay-grown floaters, commonly 3–10 cm across but occasionally larger, with compact cores of thin amber blades and, on the best specimens, one or more larger transparent twins rising from the rosette. Colour ranges from colourless and very pale yellow to rich honey amber; the most desirable pieces combine warm colour, glassy lustre, undamaged terminations, balanced “winged” form, and complete all-around development. Ordinary examples are muddy, etched, incomplete, or bruised, while top pieces show crisp edges, good transparency, and a sculptural arrangement that makes them instantly recognizable as Red River material.
“Selenite” from the Red River Floodway is the transparent to translucent collector variety of gypsum, and the locality’s fame rests on its distinctive rosettes with projecting twinned blades. The most characteristic habit begins as a ball of intersecting crystals, from which larger, clearer crystals grow outward; many of these show a broad twinned form compared by collectors to a duck’s bill. Specimens are typically miniature to small-cabinet size, with 5–9 cm floaters common in illustrated collections and larger rosettes reported from deeper, richer clay pods. Good selenite pieces here are pale yellow to amber, lustrous, undamaged, and free of excessive clay staining; under ultraviolet light many fluoresce pale blue-white to white and show a greenish phosphorescent afterglow, an effect that has become part of the locality’s identity.
Other documented material from the Red River Floodway is essentially the host sediment: clay, clay minerals, and mud associated with the gypsum rosettes. No type-locality mineral is tied to the site, and no suite of rare accessory species has emerged from the record. This is one of those localities whose importance comes from an extraordinary expression of a common mineral rather than from species diversity.
Red River Floodway selenite is frequently misdescribed in casual listings as a separate mineral from gypsum; it is gypsum, with “selenite” used as the variety or habit name. Locality labels should ideally read Red River Floodway, Winnipeg, Winnipeg Metro Region, Manitoba, Canada, and better labels may specify a controlled dig, older construction-era find, or the Block and Blady Open Pit if the provenance is reliable. Because similar clay-grown gypsum rosettes occur elsewhere, the most convincing Red River pieces combine the known locality label with the distinctive amber rosette-and-duckbill habit and strong fluorescence/phosphorescence.
Condition is the main issue. Gypsum has Mohs hardness 2, perfect cleavage, and sharp but easily bruised blade edges. Projecting twins commonly show edge nicks, cleavage bruises, dull tips, or repaired breaks. Clay in crevices is normal, but aggressive washing can reduce lustre or weaken clusters; repeated soaking, running water, and over-cleaning are poor practice. Some specimens were collected as clay-covered nodules and cleaned slowly over repeated wet-and-dry cycles. Avoid ultrasonic cleaning, acids, and any prolonged water treatment. Handle specimens by the rosette core rather than by projecting blades, and store them away from harder minerals.
Treatments and repairs deserve attention. A documented dealer note records a Red River specimen believed to have been heated or baked to create selective white areas on otherwise golden selenite, making it a human-modified piece. Modern online listings also document stabilized examples, including pieces reinforced with hot glue because of fragility. Stabilization is not automatically fatal to collectability if disclosed, especially on hidden bases or damaged undersides, but undisclosed glue, coating, dyed appearance, or baked whitening should lower confidence and value. A suspiciously chalky white termination pattern, glossy glue at the base, or overly “improved” contrast should prompt close inspection under magnification and UV.
Fluorescence is a genuine attraction here. Many Red River pieces fluoresce blue-white to white under longwave, midwave, and/or shortwave ultraviolet light and may show a green afterglow after the lamp is switched off. The response can be strong, but it should not be used as the sole proof of locality, because gypsum from other places can also luminesce. For display, UV exposure is generally safe in short sessions, but the practical risks are mechanical: dropped specimens, fingers cut by thin blades, and edges bruised during handling.
Market availability is steady but not abundant. Small rosettes and individual duckbill twins appear regularly, while fine, complete floaters with multiple projecting gemmy amber blades are scarcer and command a premium. Older, well-provenanced pieces and specimens from recognized collections have particular appeal because access is controlled and modern digging opportunities are limited. The best pieces are Canadian classics: not rare by species, but rare in the combination of clarity, habit, fluorescence, and locality history.
The best Red River Floodway collecting stories begin with the absurdity of looking for fragile crystals in a place built to move catastrophic floodwater. Ron Zeilstra’s 1998 account in Canadian Rockhound captures the old style of field work: he and Greg Hasler spent two weeks in May 1990 prospecting the banks, chasing small, hidden pods in a landscape where the crystals gave almost nothing away from the surface. They had advice from seasoned collectors—look for subtle vegetation changes and clay-colour clues—but for a week the clues mostly failed. Test pits had to reach 4 or 5 feet before anyone knew whether the effort was worthwhile. At one dry site, rosettes were present but impossible to extract cleanly, so the pit was abandoned.
The turning point came near the Trans-Canada Highway, at a proven zone close to the CN Rail trestle. Greg went alone, dropped off without a vehicle, and after only a couple of feet hit a frozen layer. If he had been able to drive away, Zeilstra thought, he probably would have quit. Instead he had eight hours before pickup, so he kept digging. The frozen layer was about 2 feet thick. After a day of work he broke through into unfrozen clay—and a pod of crystals. The next day Zeilstra returned to the site and had to watch Greg pull crystals while he was still fighting frozen ground. By the end of that day he too had broken through and was recovering rosettes.
Their tools were almost comically simple. Long straight wires—traditionally straightened coat hangers—were pushed gently into the clay until resistance suggested a crystal. The diggers then probed around the hidden object to find a safe path. As they neared a rosette, the clay changed character, peeling away in a conchoidal-looking pattern with damp faces. The goal was to leave about a centimetre of clay around the specimen as a protective jacket, then switch to trowels and toothpicks. Prying out a block was too risky; pressure could shatter the crystal. Even with care, many were lost. Each evening the clay-wrapped balls were carried home in newspaper, and the collectors cleaned them with brief lukewarm soaks, gentle water, and patient picking. If the specimen was made of blocky blades, too much water could dissolve the clayey cement between them and the rosette would fall apart.
That pit eventually reached 9 feet deep before time ran out and it was filled in. Years later, Zeilstra could still recognize the place only as a bare patch with new vegetation and a shallow indentation where the hole had been. Other pits went deeper: he later visited a site where an associate was working at 16 feet, and noted that Greg and others had brought in a backhoe for a major excavation.
A very different scene played out in August 2017, when the Winnipeg Free Press reported a temporary “mineral rush” in the floodway. The Mineral Society of Manitoba had special provincial permission to dig for three weeks, after not having been able to collect there since 2008. Bob Kitlar and Ken Fumerton were among six members working an undisclosed site with spades, garden trowels, and straightened coat hangers. Kitlar compared the work to archaeology and fishing: one person found “fish” while another found none. His warning was exact and useful: if you rush from the top downward, the crystal can “shatter like an egg.”
The 2017 dig also showed how tightly modern access is managed. A provincial spokesman confirmed that the floodway channel and adjacent land were restricted areas and that entering without permission was illegal. Jack Bauer, a former society president who organized the dig, said rain had already consumed half the collecting window by making the access road too muddy. Unlike the 2008 dig, which used only shovels, the 2017 group rented equipment to strip about half a metre of soil from the top, with the soil to be replaced afterward. Up to 30 people were listed to come out, but for safety and liability they had to be members; the public was not allowed.
The human scale of the collecting is what sticks. Danial McKay, on his first selenite hunt, worked in the clay with his wife Melissa in a neighbouring hole and called it the hardest digging he had done, harder than gravel, silt, or sand. Bauer said the largest piece found so far was about 6 centimetres across, but they were hoping for one up to 14 centimetres—“museum or monster category.” Jacques Bourgeois, then president of the society, connected the dig to Canada’s 150th birthday and called the crystals a defining feature of Red River mineral history. In that setting, the phrase feels earned: the crystals are not just pretty gypsum, but a local mineral tradition exposed by a machine-built river around Winnipeg.
