Meionite
Current inventory:  0 gems
 

  
Meionite was named in 1801 by Rene Just Haüy from the Greek word for less, in reference to the less acute pyramidal form as compared to Vesuvianite.

Discovered in 1801; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Ca₄Al₆Si₆O₂₄(CO₃)

Calcium Aluminum Silicate Carbonate

Molecular Weight:

934.71 gm

Composition:

Calcium

17.15 %

Ca

24.00 %

CaO

Aluminum

17.32 %

Al

32.73 %

Al₂O₃

Silicon

18.03 %

Si

38.57 %

SiO₂

Carbon

1.28 %

C

4.71 %

CO₂

Oxygen

46.22 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

SILICATES (Germanates)

Strunz 8th Ed. ID:

8/J.13-20

Nickel-Strunz 10th Ed. ID:

9.FB.15

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H₂O
B : Tektosilicates with additional anions

Related to:

Scapolite Group. Marialite-Meionite Series. Intermediate members are P42=n:

Members of Group:

Scapolite Group: Kembleite, Marialite, Meionite, Silvialite

Varieties:

Kembleite, Nuttallite

Synonyms:

ICSD 2628, Meyonite, PDF 44-1399, Wernerite

Crystal Data

Crystallography:

Tetragonal - Dipyramidal

Crystal Habit:

Crystals prismatic, typically with flat pyramidal terminations, striated || [001], to 0.7 m; granular, massive. 

Twinning:

None

Physical Properties

Cleavage:

Distinct on {100}{110}

Fracture:

Irregular/Uneven, Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0 - 6.0

Density:

2.74 - 2.78 (g/cm³)

Luminescence:

Commonly orange to bright yellow to red under SW and LW UV light.

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, white, grey; pink, violet, blue, yellow, orange-brown, brown; colorless in thin section.

Transparency:

Transparent to opaque

Luster:

Vitreous to pearly or resinous.

Refractive Index:

1.590 - 1.600  Uniaxial ( - )

Birefringence:

0.034 - 0.038

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

Typically in regionally metamorphosed rocks, especially marbles, calcareous gneisses, granulites, and greenschists. Also in skarns, some pegmatites, pneumatolytically or hydrothermally altered mafic igneous rocks, and ejected volcanic blocks.

Common Associations:

Plagioclase, Garnet, Pyroxenes, Amphiboles, Apatite, Titanite, Zircon

Common Impurities:

Mg, Na, K, Cl, H₂O, S

Type Locality:

Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy

Year Discovered:

1801

View mineral photos:

Meionite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Meionite is a calcium aluminum silicate carbonate mineral that is a member of the Scapolite Group of minerals that also includes Marialite. Scapolite is also considered to be the name of the series between Marialite, which is the sodium chloride rich member and Meionite, the calcium carbonate rich member. Distinguishing these two minerals from each other is difficult as they differ only slightly in density and index of refraction, increasing in both with increasing calcium content. For this reason Scapolite is the name commonly used to describe minerals and gems within the series.

Meionite was named in 1801 by Rene Just Haüy from the Greek word for less, in reference to the less acute pyramidal form compared with Vesuvianite.

Locations for Meionite: most specimens are intermediate in the series, see also marialite; some localities for highly calcic material include: at Monte Somma and Vesuvius, Campania, Italy. Around the Laacher See, Eifel district, Germany. From Pargas and Pusunsaari, Finland. At Slyudyanka, near Lake Baikal, Siberia, Russia. From Gooderham, Ontario, and Grenville, Quebec, Canada. At Rossie, St. Lawrence County, New York; Bolton, Worcester County, Massachusetts; and Cutcane Creek, Fannin County, Georgia, USA.
 

  
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