Weloganite
Current inventory:  1 gem
 

  
Weloganite was named after Sir William Edmond (W.E.) Logan (1798–1875), first Director of the Canadian Geological Survey (1840-1872).

Discovered in 1967.   IMA status: Valid (IMA approved 1968)

Chemistry

Chemical Formula:

Sr₃Na₂Zr(CO₃)₆•3(H₂O)

Hydrated Strontium Sodium Zirconium Carbonate

Molecular Weight:

814.16 gm

 Composition:

Sodium

5.65 %

Na

7.61 %

Na₂O

Strontium

32.29 %

Sr

38.18 %

SrO

Zirconium

11.20 %

Zr

15.13 %

ZrO₂

Hydrogen

0.74 %

H

6.64 %

H₂O

Carbon

8.85 %

C

32.43 %

CO₂

Oxygen

41.27 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Carbonates

Strunz 8th Ed. ID:

5/D.04-30

Nickel-Strunz 10th Ed. ID:

5.CC.05

5 : CARBONATES (NITRATES)
C : Carbonates without additional anions, with H₂O
C : With rare earth elements (REE)

Related to:

Donnayite Group.

Varieties:

None

Synonyms:

IMA 1967-042

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Crystals, roughly hexagonal, tapering, the prism faces deeply grooved and striated, withrough pyramidal terminations and a flat pedion, to 10 cm; may be massive.

Twinning:

About [103] repeated at 120º.

Physical Properties

Cleavage:

Perfect on pseudo-{0001}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

3.5

Density:

3.20 - 3.22 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Pyroelectric. May be Triboluminescent with blue light (http://www.mindat.org/mesg-6-204391.html)

Optical Properties

Color:

Lemon-Yellow, pale Yellow, Amber, commonly zoned in basal sections; Colorless in thin fragments.

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.558 - 1.646  Biaxial  ( - )

Birefringence:

0.0820 - 0.0900

Dispersion:

Weak

Pleochroism:

None

Occurances

Geological Setting:

In an alkalic sill (Francon quarry, Canada); associated with an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada).

Common Associations:

Calcite, Quartz, Dawsonite (Francon quarry, Canada)

Type Locality:

Francon quarry, Montréal, Québec, Canada

Year Discovered:

1967; IMA approved 1968

View mineral photos:

Weloganite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Weloganite is a rare carbonate mineral. Regarding gem quality crystals, it is a one locality mineral that was found at 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 rarities. The mineral is named for famous geologist, W. E. Logan, the founder of Canada's Geological Survey.

Weloganite forms as crystals that grow into tapered pseudohexagonal prisms that are often completely tapered to a point. Gems are fairly small and typically moderately included and their color can be a very attractive lemon or honey yellow.
 

  
Weloganite gems for sale: