Grossular from the Jeffrey Mine is one of the great Canadian mineral classics: sharply crystallized, lustrous, gemmy garnet from a locality better known industrially for chrysotile asbestos than for the delicate, high-color cabinet pieces that made collectors fall in love with it. The best-known Jeffrey grossular is the warm orange to sherry-colored material often sold as hessonite, but the mine also produced pink, colorless, white, pale orange, and chromium-green examples. The most desirable specimens combine transparency, bright glassy luster, crisp rhombic dodecahedral or trapezohedral form, and the unmistakable contrast of orange or pink garnets on pale to green diopside-bearing matrix.
Photo: Wikimedia Commons
Mineralogically, the Jeffrey Mine grossular belongs to the classic rodingite environment of serpentinized ultramafic rocks. The asbestos orebody consisted of serpentinized peridotite and dunite, cut by syenite, albitite, and rodingite bodies. Where calcium-rich fluids interacted with these rocks during serpentinization and rodingitization, the conditions favored calcium-aluminum silicates: grossular, diopside, vesuvianite, prehnite, pectolite, wollastonite-group minerals, and related species. This is why Jeffrey specimens so often show garnet perched on, enclosed by, or intergrown with diopside, and why the mine became famous for both grossular and vesuvianite rather than for a single species alone.
Photo: Wikimedia Commons
The visual range is unusually broad for one mine. Orange cabinet pieces with gemmy crystals to centimeter scale are the standard by which many collectors judge the locality. Pink specimens, particularly those from the 5 July 1998 find, are much rarer. Colorless to white crystals with emerald-green centers are among the most distinctive and unusual Jeffrey garnets. Chromium-bearing green grossular, often in small crystals on diopside, gives a separate collecting category with its own following. The mine’s finest pieces are not merely attractive “hessonites”; they are locality-defining specimens from one of Canada’s most prolific classic mineral deposits.
The historical weight of the locality adds to the appeal. Jeffrey began producing chrysotile in 1879, grew into one of the world’s great asbestos pits, and shaped the town formerly known as Asbestos, now Val-des-Sources. While the industrial story is complicated by the health and environmental legacy of asbestos, the specimen story is clear: during the second half of the twentieth century, miners and invited collectors recovered grossulars that became staples of Canadian suites, museum displays, and fine private garnet collections. Since the end of major operations and the flooding of important collecting areas, fresh production has essentially vanished. Today, good Jeffrey grossular is an old-stock specimen market.
Search for specimens: View all grossular specimens from Jeffrey Mine, Canada
The Jeffrey Mine is at Val-des-Sources, formerly Asbestos, in the Estrie region of Québec, Canada. In older labels and literature it commonly appears as Jeffrey Mine, Jeffrey Quarry, Johns-Manville Mine, Asbestos, Richmond County or Les Sources RCM, Québec. Serious collectors should recognize all of these label styles as potentially referring to the same classic locality, provided the mineral association and provenance are plausible.
The deposit was an open-pit chrysotile asbestos mine developed in serpentinized ultramafic rocks. The pit was described in the 2004 Mineralogical Record account as roughly 2 km in diameter and about 350 meters deep, exploiting a cylindrical asbestos orebody approximately 600 × 900 meters in plan and dipping southwest. From south to north the orebody was described as pyroxenite, serpentinized dunite, and serpentinized peridotite, against a steep slate wall. The asbestos fiber was economically concentrated mainly in serpentinized peridotite, while the celebrated grossular came from fractures in red syenite and from albitites and rodingites included within the dunite and peridotite.
For the collector, the crucial geological word is rodingite. At Jeffrey, the grossular-bearing environments formed where calcium-rich metasomatism affected igneous bodies within or adjacent to serpentinite. The resulting calc-silicate assemblages generated garnet-diopside-vesuvianite-prehnite-pectolite-wollastonite associations that are instantly recognizable in good specimens. The most classic orange grossulars commonly occur on darker syenitic or diopside-rich matrix; pink garnets from the great 1998 find are more unusual on green diopside and white albitite; chromium-bearing green grossular occurs in small, brilliant crystals, commonly with diopside and chromite-bearing assemblages.
Mining began in 1879 after chrysotile was recognized as commercially valuable in the Shipton area, and the town of Asbestos grew around the mine. The municipal history of Val-des-Sources notes a 1879 discovery of chrysotile on “La Colline Webb,” the nickname “Or Gris” for asbestos, the foundation of Asbestos in 1899, and the expansion of the mine into the town itself. Early extraction was done by hand with hammers, drills, shovels, wedges, picks, chains, horse-powered winches, hand screens, and black powder. By the twentieth century the operation had become a vast industrial pit, and its expansion forced relocation and demolition of buildings as the mine grew.
Specimen production followed the rhythm of mining rather than a collector’s calendar. When benches cut the right rodingite or syenite-bearing zones, grossular appeared; when mining moved elsewhere, the supply diminished. The 1970s and 1980s were especially important market years, when lustrous, gemmy orange Jeffrey grossular was relatively available compared with today. A new wave of discoveries between 1996 and 1999 produced several outstanding orange, pink, bicolored, and diopside-associated pieces, but by then asbestos production had already declined sharply.
Collecting access was always controlled. Public collecting inside the working mine was forbidden, though special guests, students, scientists, and escorted visitors could be admitted. Workers collected specimens despite official restrictions, especially once a profitable mineral market developed in the 1960s. For many years the mine maintained a public “mineral site” near the installations, supplied with rocks of collector interest when such material appeared in the mine. The Club de Minéralogie d’Asbestos later organized permitted collecting excursions, but instability in the pit progressively restricted access, and the last such excursions were in the early 2000s. The mine is now closed to ordinary collecting, and asbestos-bearing dumps and old mine ground should be treated as hazardous and off-limits unless access is specifically legal, guided, and properly controlled.
Production status must be read carefully because mineral labels and mining histories use different endpoints. The 2004 Mineralogical Record article describes the mine as closed in October 2002, briefly reopened for several months, and closed again in April 2003, after which pumping stopped and the pit began to flood; by July 2003 the best grossular areas were under nearly 100 meters of water. The town’s official history states that definitive industrial asbestos activity ended with the closure of the Jeffrey Mine in 2011. Other modern listings give 2012 as the final closure year, reflecting the failed attempt to revive asbestos mining after a proposed Québec loan. For mineral collectors, the practical point is that major fresh specimen production ended around the early 2000s, and present availability is overwhelmingly from old collections, dealer stock, and estate material.
Jeffrey grossular is prized for a combination of color, form, and luster that is very locality-specific. The best orange to sherry-colored crystals are glassy, transparent to gemmy, and sharply formed, typically in rhombic dodecahedra, trapezohedra, or combinations of the two. The formula of grossular is Ca3Al2(SiO4)3, and chemical work on Jeffrey material has shown near-end-member grossular compositions in some samples, with minor almandine, spessartine, pyrope, iron, manganese, and, in green material, chromium-bearing components.
Crystal faces on Jeffrey grossular often show striations and growth features. This is not a defect by itself; it is part of the locality’s character and has been studied in detail in the context of optical anomalies and growth structure. A well-preserved Jeffrey crystal may show sharply bounded rhombic faces, stepped growth features, a warm internal glow, and a vitreous surface. Collectors should distinguish natural growth striation from bruising, abrasion, or repaired face damage.
Color is a major collecting axis. The common classic hue is orange, honey-orange, cinnamon, sherry, or deep orange-red. Pink grossular is much rarer and is especially associated with the July 1998 find, where crystals reached about 1.5 cm and a very small number of top-quality specimens entered the market. Colorless, white, and pale pink crystals with green cores are another exceptional Jeffrey type; in the best examples, small emerald-green spots appear in the middle of crystal faces, creating a phantom-like bicolored effect. Chromium-bearing green grossular forms dark to bright green crystals, generally much smaller than the finest orange hessonites, but highly attractive when sharp and lustrous on contrasting diopside.
Size varies widely. Many attractive specimens show crystals in the 2–8 mm range, especially green chromium-bearing examples or druses on matrix. Fine orange hessonite-style crystals commonly occur around several millimeters to 1–1.5 cm. Important crystals can exceed 2 cm, and the literature records superb orange crystals to about 2.5 cm in late-1990s material, trapezohedral crystals to 2.1 cm from a July 2001 pocket, and a large transparent grossular crystal on matrix measuring 4.2 cm across. Such sizes are exceptional and should command close scrutiny for condition, provenance, and repair.
Associated minerals are central to recognition. Diopside is the classic companion, appearing as green crystals, pale blades, acicular sprays, or granular matrix. Prehnite occurs in globular, pseudocubic, or cream-colored forms and may accompany bicolored or pale grossular. Pectolite, clinochlore, vesuvianite, wollastonite-group minerals, chromite, heazlewoodite, albite, calcite, and rare species from the broader Jeffrey assemblage may appear depending on the pocket and rock type. Pink grossular from the 1998 discovery was associated with diopside, prehnite, fibrous wollastonite-group material, and in one described specimen a single sharp cream-colored apophyllite crystal measuring 2.7 cm.
Quality is judged first by luster and transparency, then by crystal isolation, color saturation, condition, matrix contrast, and provenance. The finest orange specimens have glowing gemmy crystals that stand proud on matrix rather than being lost in massive garnet or damaged druse. Pink specimens are judged more leniently for size because of rarity, but the top examples are still transparent, lustrous, and sharply crystallized. Green chromium-bearing material is usually valued for brightness, coverage, contrast with diopside, and clean micro-crystal development rather than large individual crystals. Colorless or green-cored examples are specialist pieces; the best have clear crystals, visible green centers, and little damage under magnification.
The first collector issue with Jeffrey grossular is locality accuracy. Older labels may say Asbestos, Jeffrey Quarry, Johns-Manville Mine, Richmond County, Estrie, or simply Québec. These are not automatically red flags, but high-value specimens should have label continuity, collection history, or a visual association consistent with Jeffrey material. Orange hessonite-like grossular from other localities can resemble Jeffrey at a glance, and green chromium-bearing garnets from other serpentinite or skarn environments can be confused with Jeffrey chromian grossular. Matrix and association matter: green or pale diopside, rodingite textures, syenitic or albititic matrix, and the characteristic glassy orange dodecahedra are important supporting clues.
There is no well-established collector problem of routinely treated Jeffrey grossular crystals comparable to the dyeing or irradiation concerns seen in some other mineral markets. Garnet is generally durable and not commonly enhanced as a specimen mineral. The more realistic risks are misattribution, exaggerated rarity language, undisclosed repairs, glued crystals, trimmed matrix, and over-optimistic variety names. “Hessonite” is a color-variety term and should not be treated as a separate species. “Chrome grossular” should ideally be supported by the color, association, and, for expensive examples, analytical confidence rather than by seller enthusiasm alone.
Condition must be checked carefully. Jeffrey grossular is hard, but crystals commonly have bruised edges, contacted faces, internal fractures, or repaired attachments because many specimens came from blasting, heavy equipment, mine dumps, or vugs opened in industrial rock. Edge contacts around the periphery are common and not necessarily serious if the main display crystals are clean. On orange cabinet pieces, examine the most prominent crystals under magnification for chips along rhombic edges and for impact bruises hidden by strong luster. On green chromium-bearing pieces, inspect the tiny crystals for abrasion, because the color can remain vivid even when many crystal tips are imperfect. On pink specimens, accept that minor peripheral contacts are common, but do not ignore damage to the principal pink crystals; the rarity of the color does not make a badly damaged piece fine.
Asbestos context matters for handling and storage. Most high-grade grossular specimens are not loose masses of chrysotile fiber, but the locality is an asbestos mine and some matrix or associated fibrous material may be suspect. Avoid sawing, grinding, air-blowing, ultrasonic cleaning, or aggressive brushing of Jeffrey material. Store friable or fibrous specimens in a closed display box, and do not handle dusty matrix casually. Collecting at the former mine or dumps is a separate legal and safety matter and should not be attempted without explicit permission and appropriate precautions.
Rarity is tiered. Small orange grossular specimens and lower-grade matrix pieces still appear with some regularity. Attractive thumbnails and miniatures with good luster remain obtainable but have become increasingly collection-to-collection material. Large, gemmy orange crystals over 1.5–2 cm, fine orange crystals on aesthetic diopside, and old 1970s–1980s cabinet pieces are much scarcer. Pink grossular from the 1998 find is genuinely rare, particularly in transparent crystals near or above 1 cm. Colorless or white crystals with green cores are rare and highly distinctive. Top green chromium-bearing miniatures with rich color and clean coverage are desirable, though generally more available than first-rank pink or large orange hessonite specimens.
The current market spans a wide range. Modest thumbnails and small specimens can still sell in the low to middle hundreds depending on condition and aesthetics; fine miniatures, rare colors, and strong old-provenance pieces can move into four figures; exceptional pink or classic gemmy orange examples may command substantially more. Recent dealer and aggregator listings show everything from inexpensive small chromian grossular thumbnails to multi-thousand-dollar hessonite and pink grossular specimens. The closed locality status, famous name, and broad collector demand for garnet all support a strong market, but value remains highly condition-sensitive.
In the late 1990s, the mine still had moments when its old magic returned. At the end of 1996 and into the first months of 1997, active workings cut a rodingite vein already known for classic orange garnets. The benching of the mine meant that this vein might only be crossed every several years, so the opportunity was brief. One pocket was not a neat geode but a series of fractures in the rock, opened by a miner operating a power shovel. Out came a small but remarkable suite: large, clear, very deep orange grossulars, almost red in tone, with acicular green diopside. The find yielded only five good cabinet specimens, two miniatures, and some lesser pieces. The miner sold the entire pocket to Montréal collector-dealer Jonathan Levinger in August 1997. Marco Amabili saw the material the same day, and after a couple of years acquired the best small-cabinet piece, 6.6 cm across, and the best miniature, 3.5 cm. The best crystals reached 2.5 cm and were described as gemmy rhombic dodecahedra on green diopside. The rest dispersed quickly into important private collections after the 1997 Denver show.
The most storied pink grossular day came on 5 July 1998, during a collecting day organized by the Club de Minéralogie d’Asbestos. Club members found what the later Mineralogical Record account called the best pink grossular garnets ever collected at the mine. The crystals were lustrous, transparent, and either floaters or set on green diopside or white albitite. That matrix was unusual: Jeffrey grossular is far more often seen on dark syenite, though exceptional orange crystals on white albitite had appeared around 1972. Amabili and Francesco Spertini dug in the albitite and recovered good pink grossular on green diopside, but the day’s memorable pocket was in a large rock found by a former Jeffrey miner. He quickly sold a large number of the pieces to Amabili. The best crystals were deep pink and reached 1.5 cm, much larger than the other pink garnets found that day and in the following weeks. They had survived blasting and collecting because they were enclosed in soft white fibrous masses of a wollastonite-group mineral. The find sold rapidly into local and international markets, but fewer than fifteen specimens were considered very high quality. No comparably important pink grossular discovery has been recorded since.
The summer of 1999 added a different kind of marvel: small, pale grossular crystals with green cores. In the best pieces, each face carried a bright emerald-green spot, regularly arranged inside the shiny transparent to pale crystals. The average crystal size was only about 4 mm, but the effect was much larger than the measurements. One crystal 9 mm across was preserved in Amabili’s collection, and at least one specimen from the find measured 10 × 20 cm. Thomas Moore had noticed two older thumbnails of similar bicolored Jeffrey grossular at the 1998 Denver show and described the optical effect as “dreamy,” the green appearing through the pinkish-orange exterior. The 1999 material gave that effect a rare starring role.
Another outstanding discovery came not in a fresh blasted pocket but from the dumps. In May 1999, a collector cracked open a large rock and exposed a cavity measuring 17 × 40 × 50 cm. The cavity was lined with green diopside crystals, some carrying orange grossular garnets perched on their terminations. The best specimen measured 7.5 × 15 cm and displayed fourteen orange garnets, each up to 1.4 cm. The lucky collector later described the discovery in Canadian Rockhound, and the best piece entered Amabili’s collection.
By July 2001, the mine was already producing far fewer mineral surprises, but a small pocket at the bottom of the pit yielded two notable miniatures with bright orange trapezohedral grossular crystals to 2.1 cm and green diopside needles. That detail matters: large trapezohedral Jeffrey grossular crystals are less common than large rhombic dodecahedra, so even a small pocket could add a distinct chapter to the locality’s record.
The final years were shadowed by the mine’s physical decline. In 1996 underground workings had been sunk into the richest part of the orebody, with production planned for 2003 or 2004, but financial problems suspended development in 2002. Open-pit operations were increasingly constrained: houses stood nearly on the lip of the pit, the workings were unstable, lateral expansion was limited, and removing overburden for deeper mining was too costly. After mining ceased and pumping stopped, water reclaimed the pit. By July 2003, the water was nearly 100 meters deep, and the best collecting areas for grossular were underwater. The directors of the Asbestos mineral club stopped excursions because of widespread slumping. The classic locality did not vanish from collections, but it did vanish as a living source.
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