The Jeffrey Mine, Asbestos, Canada

27 September 2012

The  Jeffrey  Mine,  Asbestos,  Canada

Crystal Classics and Kristalle are proud to have recently acquired a collection of superb mineral specimens from the world famous Jeffrey Mine. The collection is represented by fine wine coloured Grossular Garnets (often variety Hessonite), super specimens of green Vesuvianite, and purple Manganese enriched Vesuvianite.


A view of the Jeffrey Mine in 1972.   Photo Copyright © Rock Currier

The Jeffrey Mine is a household name amongst mineral collectors all over the world, famed for its beautiful specimens of Vesuvianite, Grossular Garnet, Pectolite and Prehnite. The mine is recorded with over a hundred valid mineral species and three type locality species i.e. Jeffreyite (Be, Al Silicate), Nisnite (Nickel-Tin alloy) and Spertiniite (Copper Hydroxide) (www.mindat.org – 2012).



Classic rich wine coloured crystals of gemmy Grossular Garnet variety Hessonite, glassy with bright luster and well formed crystal faces - BL3312

The mine is located west of the town of Asbestos in Richmond County, Quebec, Canada, south of the Nicolet River. The occurrence of a fibrous mineral was known to the native Indians and early settlers, and was used and incorporated into woollen mittens and socks. The Jeffrey Mine was first opened in 1879 for the Chrysotile, at this time the extraction of the mineral was primitive by today’s standards, and was worked by hand tools and black powder (Gun powder) - a very labour intensive process. From the late nineteenth century through the twentieth century production of Chrysotile steadily increased. The mine was a major source of fire retardant Chrysotile until recently when the pit closed in 2010.


Classic bi-coloured Vesuvianite – the purplish centres are likely coloured by the presence of Manganese - BL3324

The classic minerals found at the Jeffrey Mine are hosted in the ultramafic suite within the Serpentine Tectonic Belt. This suite includes the mineralogically important contemporaneous intruded dykes. The belt of ultramafic and associated rocks stretches north eastwards from Vermont into Quebec. The Jeffrey Mine’s Chrysotile orebodies have an overall dimension of 600m by greater than 900m and a depth of over 750m. The Dolerite dykes, some to hundreds of meters long, are the host for many of the spectacular minerals from the mine. Somewhat later the ultramafic rocks were intruded by Granitic Dykes, and along the contact margins with the ultramafic rocks they host fine specimens of Grossular and Prehnite etc. The formation of the collector minerals is believed to be the result of the hydrothermal breakdown of Olivine in the ultramafic rocks by serpentinization which released magnesium and silicon, and the breakdown of Augite and Diopside would supply the calcium and aluminium. The granitic dykes also underwent alteration, with the conversion of Hornblende to Biotite to Chlorite which initiated the release of CaO, forming the Cal-silicate species such as Diopside and Grossular.


Beautiful gemmy prismatic crystals of classic Jeffrey Mine Vesuvianite - BL3305

The Grossular Garnet specimens from the Jeffrey Mine, particularly the Hessonite variety, are probably the best from anywhere in the world. They are well known for their superb gemminess, with sharp crystal form and very bright lustre. The glassy crystals display excellent colour from colourless through pretty pale pinks, to salmon pinks to a rich deep wine colour. Very fine Grossular crystals have been cut into faceted gems with up to 24cts recorded. The crystals of Grossular from the Jeffrey Mine are dominated by the clean formation of smooth dodecahedron {110} faces and the striated trapezohedron {211} faces (the striations are actually caused by oscillating growth between the dodecahedron and trapezohedron faces). 


A great wine coloured Grossular Garnet variety Hessonite displaying the dodecahedral and trapezohedral faces to advantage. - BL3315

The classic Grossular specimens commonly display richly intergrown crystals measuring individually to 3cm. Another curiosity from the mine is the clear Grossular Garnets which envelope a core of bright green Chromium enriched Grossular Garnet. The green colouration is believed to correspond to about 7 wt % of Cr2O3 within the Grossular crystal lattice. Rich green Grossular garnets are also found at the mine with no overgrowth of clear Grossular.

A specimen depicting the bright green Chromium enriched Grossular centres enclosed by colourless to pale pink Grossular - BL3307

As well as a classic location for gemmy Grossular Garnets, the Jeffrey Mine is justly celebrated as the location for high quality specimens of Vesuvianite. The Vesuvianite crystals are sharply formed in prismatic crystals measuring to 3cm plus. Commonly they occur in excellent intergrown groups to over 30cm; displaying perfectly formed steep pyramidal terminations (many doubly terminated); or somewhat dome shaped. The fine colouration of the Vesuvianite specimens from Jeffrey Mine stands them out above many other locations. The Vesuvianite has two main colour variants -aesthetic fine green to yellowish-green, and a rich violet-purple. It can also occur as a pleasing mixture of the two colour varieties, or in a number of intermediate shades of the two dominant colours including an amber yellow. The fine violet-purple colouration is the result of a small amount of Magnesium within the crystal, and can often be a very deep colour.


A rich violet-purple acicular specimen of Magnesium Vesuvianite - BL3311

As previously mentioned the mine closed in 2010 (the general consensus as there are conflicting reports), and both the open pit and the lower underground levels are known to be flooded. There has been talk about the mine reopening for Asbestos, however it is looking unlikely due to current political considerations, so it is sad to realise that it is not likely that further specimens, especially of this beautiful quality will be found. 

 
A fine Manganese enriched Vesuvianite from the world class Jeffrey Mine - BL3327

 

Refs:

GRICE, J.D., and GASPARRINI, E. (1981) Spertiniite, Cu(OH)2 a new mineral from Jeffrey Mine, Quebec. Canadian Mineralogist, 19, 337-340.

GRICE, J.D., & WILLIAMS, R. (1979) The Jeffrey Mine, Asbestos, Quebec. Mineralogical Record, 10, 69-80.

GRICE, J.D., and ROBINSON, G.W. (1984) Jeffreyite, (Ca,Na)2(Be,Al)Si2(O,OH)7, a new mineral species and its relation to the melilite Group. Canadian Mineralogist, 22, 443-446.

ROWE, R., GRICE, J.D., POIRIER, G., STANLEY, C.J., & HORVÁTH, L. (2011) Nisnite, Ni3Sn, a new nickel mineral species from the Jeffrey mine, Asbestos, Quebec. Canadian Mineralogist 49, 651-656.

Author: Steve and Robin
Categories: Collection Acquisitions , News & Information