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The chemical formula of mineral Weloganite is indicated by Na2(Sr, Ca)3Zr(CO3)6 – 3H2O or Hydrated Sodium Strontium Calcium Zirconium Carbonate. This mineral Weloganite is actually classified under the Carbonates Mineral Class. Weloganite is only most commonly used as mineral specimen and is most often found exhibiting nice and interesting microscope images when viewed with the aid of petrographic polarizing light microscope used in the field of optical mineralogy. Mineral Weloganite is actually very rare as observed in the mineral world. It was only found at the famous Francon Quarry near Montreal Quebec, Canada. This is actually the only one site that produced good crystals but at present time, this quarry has been claimed as a landfill. For this reason, Francon Quarry is nowadays no longer producing new Weloganite specimens. This fact makes the existing Weloganite specimens true classic minerals in the mineral world. Weloganite mineral was named after the famous geologists W. E. Logan, the founder of the Canada’s Geological Survey. According to the history of Weloganite mineral, its only locality, the Francon Quarry, exposes a rare carbonatite sill. In the field of optical mineralogy, this sill which is a horizontal intrusion into parallel host rocks is usually found composed of carbonate minerals that are mostly calcite. This Quarry has been also found producing a number of rare carbonate minerals besides Weloganite. Among others include dawsonite and strontianite. In the field of optical mineralogy studies, carbonatite is an igneous rock and it is not at all that well understood by geologists in the mineral world. Carbonatite, just like other igneous rocks, starts as a molten body. However, it is composed of carbonates instead of Silicates. It will also crystallize the minerals that are more stable at higher temperatures and pressures first while leaving the difficult elements in the left over melt. In the field of optical mineralogy, difficult elements are those elements that do not fit well into a structure of a mineral because of their size and/or charge. This therefore excluded by most minerals. These elements are left to form whatever minerals they can get into as the last bit of crystallization takes place. Among these elements are strontium and zirconium.

 

            In the case of mineral 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 eventually formed bubbles or pockets. These petrified bubbles were actually found coated in exotic minerals some of which were never before known to science when the excavations at the Francon Quarry uncovered the sill. It was however believed that this unusual sill was somehow allowed to cool much more slowly than other carbonatite sills. It is actually 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. However, the difficult elements are incorporated into commoner minerals as trace elements. Mineral Weloganite is usually found forming attached crystals that grow into tapered pseudohexagonal prisms that appear more fascinating when viewed with the aid of polarizing microscopes used in the field of optical mineralogy. Weloganite crystals are occasionally complexly tapered. They are usually found growing wider and thinner several times before terminating to either a point or a flat pedial face that can be found more clearly visible when viewed with the aid of polarizing microscopes used in optical mineralogy. The color that can be found exhibited by the mineral is muted amber that appears more interesting when viewed with the aid of polarized microscope. This can actually enhance the already interesting, rare and classic crystals of mineral Weloganite.

             Mineral Weloganite is most commonly found white, yellowish or amber color that would appear more interesting and more splendidly exhibited when viewed with the aid of polarizing microscopes used in optical mineralogy. Weloganite is most commonly found exhibiting a vitreous to chalky luster when viewed in reflected light of petrographic polarizing microscopes used in optical mineralogy. Most crystals of mineral Weloganite are found translucent, rarely transparent in appearance. Weloganite is also known to crystallize in the triclinic system of crystal formation. In optical mineralogy, this triclinic crystal system commonly comprises crystals having three axes, of which all are unequal in length and are positioned oblique to one another. The crystal habit of the mineral Weloganite as described in the field of optical mineralogy usually include pseudohexagonal prisms that often tapper to a point or are terminated by a pedial face. It can be found that from their point of attachments, the crystals will usually taper to a wider width before tapering to their terminations or repeatedly tapering wider and thinner before terminating.              The hardness measure of mineral Weloganite when it is evaluated using the Mohs scale method is usually found 4. Weloganite mineral has one distinct cleavage found in only one direction which can be found more clearly visible when the specimen is evaluated closely with the aid of petrographic polarizing microscope used in optical mineralogy. The specific gravity measure of the mineral is usually found 3.2 grams per cubic centimeters, which is considered slightly above average for transparent minerals. Weloganite is also found showing conchoidal fracture when evaluated with the aid of polarizing light microscope for mineralogists. Weloganite is also most commonly found leaving a white streak when specimen sample is rubbed on a white porcelain streak plate. Mineral Weloganite is also found heavily striated or repeatedly notched vertically which can be seen more clearly visible when closely evaluated with the aid of polarizing microscopes for mineralogists. The best field indicators of mineral Weloganite usually include crystal habit, locality, color and striations. Weloganite is also most commonly found associated with other minerals including calcite, strontianite and dawsonite. Weloganite notably occurs at its type of locality at the Francon Quarry, Montreal, Quebec, Canada and at a few other rare locations.



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Friday, October 30th, 2009 at 2:56 pm
Category:
The Carbonates and Borates Mineral Class
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