A collector's guide to Jeffrey Quarry, null: its geology, mining history and notable minerals, illustrated with the 24 specimens documented from this locality on EarthWonders.
Key facts
Jeffrey Quarry is the collector’s name many older labels use for the Jeffrey Mine at Val-des-Sources, formerly Asbestos, in Québec’s Estrie region. Industrially it was a great chrysotile-asbestos open pit; mineralogically it became one of Canada’s defining specimen localities because the asbestos orebody was cut by altered dykes and rodingite zones that made an extraordinary calcium-silicate suite. In those narrow altered rocks, grossular, vesuvianite, prehnite, diopside, pectolite, wollastonite-group minerals, and late copper- and nickel-bearing rarities formed in cavities, joints, and contact zones within serpentinized ultramafic rock. The best specimens have a look that is immediately recognizable: glassy orange or pink grossular on green diopside, deep violet to purple-capped vesuvianite crystals, pale to lavender prehnite perched on sparkling garnet, and occasional chromian greens so saturated they seem out of place in an asbestos mine.
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The locality’s historical importance is twofold. First, the mine was one of the giant chrysotile producers of the 20th century, an open pit that shaped the town physically, economically, and socially. Second, it was a mineral-specimen factory of rare quality. By the 1970s and 1980s, Jeffrey grossular had become a classic North American garnet; by the late 1990s and early 2000s, new pockets of pink grossular, chrome-green vesuvianite, purple-capped vesuvianite, and exceptional prehnite reinforced the mine’s reputation just as large-scale mining declined and then ended. Because the richest specimen zones were tied to limited benches, dykes, and pockets exposed only when mining crossed the right ground, the supply has always been episodic; today, fine Jeffrey material is largely a matter of old collections, miner pieces, dealer stock, and careful estate finds.
Photo: Wikimedia Commons
Photo: Wikimedia Commons
Search for specimens: View all specimens from Jeffrey Quarry, null
The Jeffrey deposit is a chrysotile-asbestos orebody hosted by serpentinized ultramafic rocks, principally peridotite and dunite, in the Québec ophiolitic belt of the Eastern Townships. The economic ore was a stockwork of chrysotile fibre veins in serpentine; cross-fibre veins supplied much of the ore, with additional slip fibre seams and mass-fibre occurrences. Serpentinization produced lizardite-dominant serpentinite with antigorite and brucite also noted in mine studies, while magnetite, brucite, talc, picrolite, and related serpentine minerals formed part of the broader asbestos assemblage.
For collectors, the important rocks were not the chrysotile-bearing serpentinites themselves but the dykes and rodingitized intrusive bodies that cut them. Historical geological reports describe red and grey “granitic” to dioritic dykes, albitite, syenitic material, and rodingite within the serpentinized peridotite and dunite. Along dyke contacts, fractures, joints, and cavities, hydrothermal alteration and calcium metasomatism generated grossular, vesuvianite, diopside, and prehnite. This is the key to Jeffrey specimens: the mine’s best collector minerals are contact- and cavity-grown calcium silicates formed where chemically reactive intrusive rocks met serpentinized ultramafic host rock.
The famous orange to pink grossular came from several zones rather than a single permanent collecting face. Many classic pieces show garnet on dark syenitic or altered intrusive matrix, commonly with green diopside. Unusual finds placed grossular on white albitite or in soft fibrous wollastonite-group masses, and those matrices often protected crystals from blast damage. Diopside is more than an accessory at Jeffrey: green acicular sprays, white needles, and tabular colorless crystals served as the architectural matrix for some of the most celebrated grossular, prehnite, and vesuvianite specimens.
The mine’s vesuvianite story is especially tied to rodingite in the southeast part of the pit, near the former 2440 level. Purple, pink, yellow, and green vesuvianite crystals were found in a rodingite dyke enclosed in serpentinized dunite, parallel to the large shear zone at the southeast limit of the orebody. Traces of purplish acicular vesuvianite were reportedly observed during geological mapping in 1950, major finds followed in 1978, 1979, and 1988, and renewed access in 2002–2003 produced some of the best late Jeffrey vesuvianite ever marketed. In that zone, pockets only a few centimetres apart could yield different morphologies and colors, explaining why Jeffrey vesuvianite ranges from pale green prisms with purple caps to deep chromian green crystals and violet to amethyst-colored clusters.
Mining began after asbestos was identified on the property in the late 19th century. William Henry Jeffrey financed early work on the deposit, and the property later passed through more modern corporate ownership, including Asbestos and Asbestic interests and then Canadian Johns-Manville. The mine was worked as a large open pit for most of its life, with an underground phase beginning around 1950 and ending in the early 1960s when changes in open-pit equipment and economics favored surface mining again. By the late 1960s and early 1970s, the pit had become immense: thousands of feet long and wide, hundreds of feet deep, and expanding into the townscape. Later operators included JM Asbestos Inc. and Jeffrey Mine Inc.; by the early 2000s, asbestos-market decline, financial trouble, instability, and flooding had effectively ended the great specimen-producing era.
Collecting access was never a simple public-free-for-all. Public collecting on mine property was forbidden, though students, scientists, special guests, miners, and organized club trips obtained access under controlled conditions. Miners had a major role in specimen recovery, particularly during the period when the market for grossular and other Jeffrey minerals made good pieces worth saving from the shovel, crusher, or dump. The Club de Minéralogie d’Asbestos organized permitted collecting excursions beginning in the 1990s, but after 2001 the collecting area was restricted because of pit instability, and the last published accounts of club collecting in the open pit date to the early 2000s. As the pit flooded, the best lower grossular areas disappeared underwater. The former mine site is now a redeveloping municipal and heritage landscape with official viewpoints and guided tourism activities, not an open collecting locality.
The most famous documented specimen events include the deep orange grossular pocket sold by a miner in August 1997; the 5 July 1998 collecting-day discovery of exceptional deep pink grossular on green diopside and white fibrous wollastonite-group material; the 1999 find of pale, colorless, and pink grossular crystals with vivid green cores; cream-colored pseudocubic prehnite found in 2000; orange trapezohedral grossular from a small pocket at the bottom of the pit in July 2001; and a succession of 2002–2003 vesuvianite pockets in the southeast rodingite zone, including chrome-green single crystals, yellow-green clusters with purple cores, and the celebrated purple-cap material.
Jeffrey vesuvianite is among the locality’s signature species, especially the material from rodingite in the southeast part of the pit near the former 2440 level: sharp prismatic crystals in pale green, yellow-green, pink, violet, purple, and deep chromian green, with the finest specimens showing bright glassy luster, transparent zones, complex terminations, or strong zoning such as pale green prisms with deep purple “caps.” Published late finds include loose translucent chrome-green crystals to about 4.4 cm, clusters with crystals to about 3 cm from the August 2002 pocket, forest-green crystals with pointed terminations to about 4.5 cm, and multicolored cabinet specimens; top pieces are judged by color saturation, undamaged terminations, isolation or all-around crystallization, and the difficult combination of size, transparency, and vivid Jeffrey color.
Prehnite from Jeffrey is unusually important because the mine produced distinct, well-formed crystals rather than only the more familiar botryoidal or crusty habit: cream, colorless, white, pale yellow, green, and rare purple to lavender examples occur as blocky, steep pyramidal, pseudocubic, chisel-like, or curved aggregates, commonly with grossular, diopside, pectolite, and vesuvianite. Documented finds include cream-colored pseudocubic crystals exceeding 1.3 cm on edge associated with acicular white diopside in 2000, pale pink grossular specimens with globular cream prehnite from 1999, and rare lavender manganoan prehnite on green grossular matrix with crystals reported to about 3 cm; the best specimens show distinct crystal form, separation from matrix, clean luster, uncommon color, and strong contrast with green garnet or diopside.
Grossular made Jeffrey famous long before the late vesuvianite boom: lustrous dodecahedra, trapezohedra, and combinations in orange hessonite, deep orange-red, pink, colorless to white, and green chrome-bearing varieties occur on altered dyke rock, diopside, albitite, and fibrous wollastonite-group material. Classic orange pieces are usually prized for gemminess and contrast with green diopside; the 1997 pocket yielded only a few top cabinet pieces and miniatures with deep orange crystals to 2.5 cm, while the 5 July 1998 collecting day produced the best deep pink crystals, to about 1.5 cm, in protected fibrous matrix. Exceptional single crystals can exceed typical cabinet expectations for the locality, but most fine Jeffrey grossular is measured less by sheer size than by transparency, sharp form, color intensity, undamaged faces, balanced matrix, and recognizable Jeffrey associations.
Beyond the three headline species, Jeffrey’s collector suite includes diopside, pectolite, wollastonite-group minerals, chrysotile, brucite, magnetite, heazlewoodite, awaruite, shandite, chromite, native copper, chalcocite, atacamite, apophyllite-group minerals, albite, xonotlite, pumpellyite, zoisite, and many rarities. Its scientific importance is strengthened by type-locality minerals: spertiniite, Cu(OH)2, named for mine geologist Francesco Spertini and found as tiny blue to blue-green lathlike aggregates associated with chalcocite, native copper, and atacamite in rodingite; jeffreyite, a calcium-sodium beryllium silicate related to the melilite group; and nisnite, Ni3Sn, described from re-examined heazlewoodite-bearing rodingite material. Those species are generally microscopic or specialist material, but they make Jeffrey more than a cabinet-specimen locality: it is also a serious reference locality for rodingite mineralogy.
Jeffrey specimens are widely collected and widely labeled under several historically correct names: Jeffrey Mine, Jeffrey Quarry, Johns-Manville Mine, Asbestos, Richmond County, Les Sources RCM, and Val-des-Sources. Older labels reading simply “Asbestos, Quebec” are common and may be perfectly legitimate, but the mineral association should make sense. Orange or pink grossular with green diopside, purple or green vesuvianite from rodingite, crystallized prehnite on garnet or diopside, and pectolite-diopside assemblages fit the locality well. Generic green garnet, unattributed “hessonite,” or loose vesuvianite crystals without provenance deserve more scrutiny, especially when the color and crystal habit resemble other rodingite or skarn localities.
The chief authenticity issue is mislabeling, not treatment. There is no well-established tradition of dyed, heated, or otherwise treated Jeffrey grossular, vesuvianite, or prehnite in the collector market. However, fine loose crystals and trimmed thumbnails can be difficult to evaluate without old labels or collection history. Jeffrey grossular should not be assumed to be hessonite solely because it is orange; green material may involve chrome-bearing grossular or andradite-variety demantoid associations at the broader locality, so serious pieces benefit from accurate species identification when color or composition matters.
Condition is critical. Grossular crystals commonly show bruised dodecahedral edges, contacted backs, embedded fibrous material, or tiny chips from blasting and pocket extraction. Vesuvianite may have abraded terminations, repaired-looking contact areas that are actually natural growth interference, or matrix instability where massive vesuvianite and rodingite are friable. Prehnite crystals from Jeffrey can be surprisingly sharp but are vulnerable at the tapered terminations and along protruding edges. The most desirable pieces are not necessarily the largest; they are the ones with clean terminations, strong contrast, minimal blast damage, and an old, convincing provenance.
Handling deserves special caution because this is an asbestos mine locality. Many Jeffrey specimens consist of stable silicates and are safe to display when intact and undisturbed, but pieces with visible chrysotile, loose fibrous serpentine, dusty serpentinite matrix, or friable mine-dump material should not be brushed, trimmed, air-blown, sawn, or cleaned aggressively. Keep potentially fibrous specimens boxed or in a sealed display environment, avoid creating dust, and use appropriate respiratory protection and wet methods if professional preparation is absolutely necessary. For most collectors, the safest approach is to buy well-prepared, stable specimens and leave any fibrous matrix untouched.
Market availability is finite. Jeffrey was once abundant enough that thumbnails, miniatures, and small cabinets appeared regularly from miners, club collecting, and Canadian dealers. Since the closure and flooding of the pit, fresh supply has essentially stopped, and fine pieces have moved steadily into established collections. Good thumbnails still appear, especially grossular and vesuvianite, but top pink grossular, purple-cap vesuvianite, deep chrome-green vesuvianite, crystallized lavender prehnite, and old-cabinet specimens with excellent labels are increasingly competitive.
In August 1997, one of the great late grossular episodes began not with a formal dig but with a miner operating a power shovel. A series of fractures opened in the rock and produced a tiny number of superb specimens: deep orange, almost red, transparent grossular crystals on acicular green diopside. The published account is almost painful in its scarcity—only five good cabinet specimens and two miniatures, plus lower-grade pieces. The miner sold the entire lot to Montréal collector-dealer Jonathan Levinger, and by the Denver show that year the surviving top pieces had already begun dispersing into serious private collections. The best small-cabinet example measured 6.6 cm wide and carried gemmy rhombic-dodecahedral grossular crystals up to 2.5 cm, the kind of combination that defines Jeffrey at its most elegant: orange fire lifted on green needles.
The next summer produced a very different color. On 5 July 1998, during a collecting day organized by the Club de Minéralogie d’Asbestos, club members found the mine’s best known pink grossular. The setting mattered. Pink Jeffrey garnets had been known, but these were lustrous, transparent crystals—some floaters, some on green diopside, some on unusual white albitite matrix rather than the darker syenitic matrix collectors expected. The most memorable pocket was found in a large rock by a former Jeffrey miner, who sold many of the pieces immediately to Marco Amabili. The garnets were deep pink and reached about 1.5 cm, larger and better than other pink crystals collected that day and in the following weeks. Many had been enclosed in soft white fibrous wollastonite-group masses, which cushioned the crystals through blasting and recovery. Fewer than 15 were considered very high quality, and no comparable pink grossular find followed.
In 1999, Jeffrey offered another variation on the garnet theme: pale pink, colorless, or white grossular with green cores. On the finest examples, each crystal face showed a bright green center seen through a pale outer layer, producing a regularly spaced internal glow. The average crystal size was only about 4 mm, with a single 9 mm crystal noted in one collection, but the optical effect made the pieces memorable. Some were associated with cream-colored globular prehnite, and at least one large specimen measured about 10 x 20 cm. These are the sort of Jeffrey specimens that can be overlooked in a case beside larger hessonite—until light catches the green centers and the whole surface seems to blink.
The vesuvianite revival of 2002 had the atmosphere of a second chance. After pit instability restricted collecting to a small safe area in the upper east portion, collectors found themselves back near ground that had already produced important vesuvianite in 1978 and 1988. The rodingite dyke had been partly covered during mine expansion, but slumping exposed a section beside a secondary mine road. In May 2002, in “awful weather conditions,” collectors found pink and purple transparent crystals with shiny pink terminations and pale-green prism faces. The finds continued through the summer. In July and August, deep chromian green vesuvianite crystals—emerald to dioptase-green—were recovered from small vugs in a thin emerald-green vein within the main pale-green vesuvianite vein. The best loose crystals reached about 4.4 cm long and nearly 1 cm wide.
On 25 August 2002, two collectors struck one of the most productive vesuvianite pockets of the late period. More than 100 specimens of yellowish green vesuvianite came out, some with purple cores. The pocket yielded thumbnails, miniatures, cabinets, and a large specimen around 25 x 35 cm. A cluster of doubly terminated crystals, with individual crystals to about 3 cm long and 1 cm wide, was among the standout pieces. The pocket was filled with fine granular vesuvianite, so many specimens came away essentially as floaters rather than as broken fragments off solid matrix. In the following weeks miners collected additional top pieces with a power shovel until management bulldozed over the collecting site.
Jeffrey’s final vesuvianite chapter in 2003 was narrower but still brilliant. A 12.6 cm cluster of partly gemmy purple-yellow-green crystals, including a sharp multicolored crystal measuring about 1.4 x 1.6 x 6 cm, was singled out as one of the best vesuvianite specimens ever found at the mine. Collectors also recovered the classic pale green crystals with deep purple, shiny, flat terminations—the “purple-cap” vesuvianites—and forest-green pointed crystals to about 4.5 cm. One 6 cm group of deep amethyst-colored vesuvianite stood out for color. The striking fact is how confined the producing area was: all those forms and colors came from a zone only about 40 meters long, with pockets just centimeters apart yielding visibly different crystals.
The collecting culture at Jeffrey was as distinctive as the minerals. Public collecting inside the mine was officially forbidden, and even miners were not supposed to collect specimens, yet miners began saving minerals seriously in the 1960s as demand for grossular grew. For a quarter century, mine management maintained a “mineral site” near the installations where the public could collect from rock brought out of the mine rather than sent to the dumps. When interesting mineralized rock appeared, pieces were trucked to the site, and countless visitors found something worth keeping. Later, the organized club excursions became the only practical route into the pit for collectors. The last such excursions occurred just as the mine was becoming too unstable and too flooded for safe collecting.
One of the strangest coda moments in the mine’s history came after the October 2002 closure. A NASA contractor arranged for the mine to reopen briefly to obtain special-quality asbestos for space shuttle seals. The reopening lasted only a few months, and by April 2003 the mine closed again. When pumping stopped, the pit began filling. By July 2003 the lower workings were flooded to nearly 100 meters, and the best grossular collecting areas were underwater. That image—the great garnet ground drowned beneath blue-green water—helps explain why even small, well-labeled Jeffrey specimens now carry a sense of finality.
