Axinite-(Mg)  (Magnesio-Axinite)
Current inventory:  0 gems
 

  
Axinite-(Mg) is named from the Greek word axina for axe, in allusion to the common habit of its crystals, and the magnesium dominance in the formula.

Discovered in 1975;  IMA status: Valid (IMA approved 1975)

Chemistry

Chemical Formula:

Ca₂MgAl₂BSi₄O15(OH)

Calcium Magnesium Aluminum Boron Sorosilicate Hydroxide

Molecular Weight:

538.57 gm

Composition:

Calcium

14.88 %

Ca

20.82 %

CaO

Magnesium

4.51 %

Mg

7.48 %

MgO

Aluminum

10.02 %

Al

18.93 %

Al₂O₃

Silicon

20.86 %

Si

44.62 %

SiO₂

Boron

2.01 %

B

6.46 %

B₂O₃

Hydrogen

0.19 %

H

1.67 %

H₂O

Oxygen

47.53 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/E.06-10

Nickel-Strunz 10th Ed. ID:

9.BD.20

9 : SILICATES (Germanates)
B : Sorosilicates
D : Si₂O₇ groups, with additional anions; cations in tetrahedral [4] and greater coordination

Related to:

Axinite Group. Axinite-(Fe)-Axinite-(Mg) Series. Magnesium analog of Axinite-(Fe) and Axinite-(Mn)

Members of Group:

Axinite Group: Axinite-(Fe), Axinite-(Mg), Axinite-(Mn), Tinzenite

Varieties:

n/a

Synonyms:

IMA1975-025, Magnesio-Axinite, Magnesium Axinite

Crystal Data

Crystallography:

Triclinic - Pedial

Crystal Habit:

As crystals, to 3 cm, with the axe-head-shaped morphology typical of axinites; originally found as a rough gemstone.

Twinning:

None

Physical Properties

Cleavage:

Good on {100}, poor on {001}, {110}, and {011} (by analogy to the axinite group)

Fracture:

Uneven to Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.5

Density:

3.178 (g/cm³)

Luminescence:

Fluoresces red-orange in LW UV, duller red in SW UV

Radioactivity:

Not Radioactive

Optical Properties

Color:

Pale Blue to pale Violet; light Brown to light Pink

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.656 - 1.678  Biaxial ( + ) or ( - )

Birefringence:

0.0090 - 0.0110

Dispersion:

Strong; r > v

Pleochroism:

Pale blue to pale violet and pale gray

Occurances

Geological Setting:

Typically a mineral formed during contact metamorphism and boron metasomatism.

Common Associations:

Epidote, Tremolite, Calcite (London Bridge, Australia); Prehnite, Epidote, Actinolite, Vesuvianite (Luning, Nevada, USA)

Common Impurities:

Ti, V, Mn, Zn, K, H₂O

Type Locality:

Merelani Hills (Mererani), Lelatema Mts, Arusha Region, Tanzania

Year Discovered:

1975; IMA approved 1975

View mineral photos:

Axinite-(Mg) Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Magnesio-Axinite was renamed Axinite-(Mg) by Mineralogical Record v39 (2008). Axinite-(Mg) is the very rare magnesium analog of Axinite-(Fe), or Ferro-Axinite which is the iron anolog. Axinite-(Mg) was discovered in 1975 in the Merelani Hills of Tanzania. It ranges in color from pale blue to pale violet to more of a deep violet and is rarely very clean. Crystals, and therefore gems, are typically translucent due to inclusions. Axinite-(Mg) fluoresces red-orange in LW UV, duller red in SW UV.

Axinite-(Mg) is only found at a few localities worldwide including the type locality at the Merelani Hills, Lelatema Mountains, Arusha Region, Tanzania; at London Bridge, near Queanbeyan, New South Wales, Australia; Yankee Hill, Butte County, California, USA; Luning area, Santa Fe district, Mineral County, Nevada, USA.
 

  
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