• Chemistry: Na2(Sr, Ca)3Zr(CO3)6 - 3 H2O, Hydrated Sodium Strontium Calcium Zirconium Carbonate.
  • Class: Carbonates
  • Uses: Only as mineral specimens.
  • Specimens

Weloganite is a rare carbonate mineral. It was found at only one site that produced good crystals, the famous Francon Quarry near the city of Montreal, Quebec, Canada. The quarry has now been reclaimed as a landfill and is not producing any new specimens, making existing specimens true classics. The mineral is named for a famous geologist, the founder of Canada's Geological Survey, W. E. Logan.

The Francon quarry exposes a rare carbonatite sill. The sill, a horizontal intrusion into parallel host rocks, is composed of carbonate minerals, mostly calcite. The Francon Quarry has produced a number of rare carbonate minerals besides weloganite such as strontianite and dawsonite. Carbonatite is an igneous rock and is not all that well understood by geologists.

Like other igneous rocks, the carbonatite starts as a molten body, but is composed of carbonates instead of silicates. Like other igneous rocks, carbonatites will crystallize the minerals that are more stable at higher temperatures and pressures first, leaving difficult elements in the left over melt. Difficult elements are those elements that because of their size and/or charge do not fit well into a mineral's structure and are therefore excluded by most minerals. These elements, like strontium and zirconium, are left to form whatever minerals they can get into as the last bit of crystallization takes place.

In the case of weloganite, the sill had already formed most of its minerals when fluids rich in difficult elements and volatile gases rose to the top of the sill and formed bubbles or pockets. When the excavations at the Francon Quarry uncovered the sill, these "petrified" bubbles were found coated in exotic minerals some of which were never before known to science. It is believed that this unusual sill was somehow allowed to cool much more slowly than other carbonatite sills. It is the time to differentiate the difficult elements that may have made the difference in producing these wonderful minerals. Other carbonatite sills have similar chemistries to the Francon Quarry sill but the difficult elements are incorporated into commoner minerals as trace elements.

Weloganite forms attached crystals that grow into tapered pseudohexagonal prisms. The crystals are occasionally complexly tapered, growing wider and thinner several times before terminating to either a point or a flat pedial face. The color can be a muted amber color and can enhance these already interesting, rare and classic crystals.


  • Color is white, yellowish or amber.
  • Luster is vitreous to chalky.
  • Transparency crystals are translucent, rarely transparent.
  • Crystal System is triclinic; bar 1
  • Crystal Habits include pseudohexagonal prisms that often tapper to a point or are terminated by a pedial face. From their attachment points the crystals will usually taper to a wider width before tapering to their terminations or repeatedly tapering wider and thinner before terminating.
  • Hardness is 4
  • Specific Gravity is 3.2 (slightly above average for transparent minerals)
  • Cleavage is distinct in one direction.
  • Fracture is conchoidal.
  • Streak is white.
  • Other Characteristics: heavily striated or repeatedly notched vertically.
  • Associated Minerals include strontianite, dawsonite and calcite.
  • Notable Occurrences include Francon Quarry, Montreal, Quebec, Canada and only at a few other rare locations.
  • Best Field Indicators are locality, crystal habit, striations and color.
WELOGANITE specimens:
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WELOGANITE specimen wel-1
$ 40.00
Dims: 2.5" x 2.0" x 1.9" (6.4 x 5.1 x 4.8 cm)
Wt: 4.14 oz. (117.3 g)
Francon Quarry, Montreal, Quebec, Canada
THis interesting little specimen consists of a host rock that is known as carbonatite. I believe that it is made up of a variety of carbonate minerals, both common and rare. Inside a hollow in this material rest several crystals of Weloganite, an uncommon complex carbonate of several different metals that occurs in crystal form at only one locality, a mine near Montreal, Canada, that is now closed. These crystals are in very good condition, though a few of them show signs of damage. They occur in a hexagonal prismatic form with basal terminations, and range in length from 2 or 3 mm to almost 1 cm. Their prism faces are heavily striated parallel to the basal plane. They have a gray-white color and a dull luster, and are dimly translucent. They are accompanied by what appear to be several gray-white calcite crystals with a dull luster. Their striations and rather uneven form remind me of that of some sapphire crystals.
no photo
wel-1 ($ 40.00)
Francon Quarry, Montreal, Quebec, Canada
WELOGANITE specimen wel-2
$ 150.00
Dims: 2.6" x 2.4" x 1.6" (6.6 x 6.1 x 4.1 cm)
Wt: 6.46 oz. (117.3 g)
Francon Quarry, Montreal, Quebec, Canada
This hand specimen consists of several hexagonal prismatic Weloganite crystals resting on a thick slab of carbonatite host rock. The crystals are in moderately good condition, as some of them show noticeable to severe damage. They do not exceed 0.9" (2.3 cm) in length, and tend to have rather warped and inconsistent forms. All have a pale greenish-yellow coloration and a pearly-to-waxy luster, and are translucent. It would appear that there are many crystals that are mostly buried under scores of small, round, white nodules that rest among the Weloganites- I don't know what these nodules are made of, but it would be reasonable to assume that it would be a carbonate mineral of some sort. This is only the second Weloganite specimen that I have seen in my travels.
no photo
wel-2 ($150.00)
Francon Quarry, Montreal, Quebec, Canada
WELOGANITE specimen wel-3
$ 90.00
Dims: 3.8 x 2.0 x 1.8" (9.7 x 5.1 x 4.6 cm)
Wt: 7.60 oz. (215.5 g)
Francon Quarry, Montreal, Quebec, Canada
This hand specimen consists of several hexagonal prismatic Weloganite crystalsAt least 7 small Weloganite crystals rest in a hollow in the dull, pale gray host rock of this small hand specimen. None of them have dimensions that exceed 0.2" (5 mm), but they are generally in very good condition- only one of the crystals is damaged, and it has been broken off near its base. All have slighty-warped but relatively well-defined hexagonal prismatic form, with well-defined edges and disjointed and striated but clean faces that possess a flat, matte luster. Their color is a uniform gray-white, and all are completely opaque. There are several long, thin bladed crystals accompanying the Weloganites- they have a milky white coloration and are translucent, but I cannot identify them. I would guess that they might possibly be made of artinite.
no photo
wel-3 ($ 90.00)
Francon Quarry, Montreal, Quebec, Canada


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