Katophorite (Ferri-Katophorite, Ferro-Katophorite, Magnesio-Katophorite, etc.)
Current inventory:  0 gems
 

  
Katophorite is named from the Greek word κατώφορος (kataphora) meaning carrying down, in allusion to its volcanic origin. "Ferri-" and "Ferro-", etc. were added in 2012 as part of an IMA redefinition of the Katophorite Root Name Group due to its iron content.

Discovered in 1894; IMA status: Valid (IMA Approved 1997; redefined by IMA in 2012)

Chemistry

Chemical Formula:

Na[NaCa][(Fe²⁺,Mg)₄Al](Si₇Al)O₂₂(OH)₂

Sodium Calcium Iron Magnesium Aluminum Silicate Hydroxide

Emperical Chemical Formula:

Na_1.2K_0.3Ca_1.3Fe²⁺_3.25Mg_1.5Ti_0.2Mn²⁺_0.2Al_0.7Si_7.3O₂₂(OH)₂₂

Molecular Weight:

939.86 gm

Composition:

Potassium

1.25 %

K

1.50 %

K₂O

Sodium

2.94 %

Na

3.96 %

Na₂O

Calcium

5.54 %

Ca

7.76 %

CaO

Magnesium

3.88 %

Mg

6.43 %

MgO

Titanium

1.02 %

Ti

1.70 %

TiO₂

Manganese

1.17 %

Mn

1.51 %

MnO

Aluminum

2.01 %

Al

3.80 %

Al₂O₃

Iron

19.31 %

Fe

24.84 %

FeO

Silicon

21.81 %

Si

46.67 %

SiO₂

Hydrogen

0.21 %

H

1.92 %

H₂O

Oxygen

40.86 %

O

100.00 %

100.09 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/F.09-30

Nickel-Strunz 10th Ed. ID:

9.DE.20

9 : SILICATES (Germanates)
D : Inosilicates
E : Inosilicates with 2-periodic double chains, Si₄O₁₁; Clinoamphiboles

Related to:

Katophorite Root Name Group > Sodium-Calcium Amphibole Subgroup > w(OH, F, Cl)-dominant Amphibole Group > Amphibole Supergroup. Ferri-Katophorite - Magnesio-Katophorite Series

Members of Group:

Katophorite Root Name Group: Ferri-Katophorite, Ferri-fluoro-Katophorite, Ferro-Katophorite, Fluoro-Katophorite, Katophorite, Magnesio-Katophorite, Potassic-ferri-Katophorite, Potassic-ferri-Katophorite, Potassic-fluoro-Katophorite

Varieties:

Ferri-Katophorite, Ferri-fluoro-Katophorite, Ferro-Katophorite, Fluoro-Katophorite, Katophorite, Magnesio-Katophorite, Potassic-ferri-Katophorite, Potassic-ferri-Katophorite, Potassic-fluoro-Katophorite

Synonyms:

Cataphorite, IMA2013-140, Magnesio-Katophorite

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Prismatic, granular, also as fibrous aggregates or dendrites and skeletal crystals. Commonly rimming other minerals. 

Twinning:

|| {100}

Physical Properties

Cleavage:

Perfect on {110}, intersecting at ~56° and ~124°; parting on {010}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0 - 6.0

Density:

3.2 - 3.5 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Black, dark green-black, bluish black; reddish yellow, bluish green in thin section

Transparency:

Transparent to translucent, opaque

Luster:

Vitreous

Refractive Index:

1.640 - 1.692  Biaxial ( - )

Birefringence:

0.020

Dispersion:

Strong, r < v

Pleochroism:

Strong; reddish yellow, reddish brown, and dark green to black

Anisotropism:

n/a

Occurances

Geological Setting:

In alkalic volcanic and plutonic igneous rocks; in blueschist facies jadeitites.

Common Associations:

Arfvedsonite, Aegirine, Nepheline, Pyroxenes, Eckermannite, Chromite

Common Impurities:

n/a

Co-Type Localities:

• Ferro-Katophorite: first described by W.C. Brøgger (1894) as an amphibole mineral which he found at three localities in the Permian Oslo Region, Norway:
a) from a grorudite outcrop at Grussletten, Grorud, Oslo;
b) from sølvbergite along the Kjose-Oklungen Railway, Vestfold;
c) and from a sølvbergite boulder found in Lågendalen, Vestfold
• Katophorite: Hpakant-Tawmaw Jade Tract, Hpakant Township (Hpakan; Phakant; Phakan), Mohnyin District (Moe Hnyin District), Kachin State, Burma (Myanmar)  

Year Discovered:

• Ferro-Katophorite: 1894
• Katophorite: 2013

View mineral photos:

Katophorite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

The Katophorite minerals are sodium-calcium Amphiboles with varying amounts of magnesium (Mg), iron (Fe) and alumiunum (Al). The varieties of Katophorite are named according to their chemical composition. Examples are: Ferri-Katophorite is named for its ferric iron dominance; Ferro-Katophorite is named for its ferrous iron dominance; Magnesio-Katophorite is named for its magnesium dominance, and so on. At this time there are nine varieties with Katophorite as their base name with various element name modifiers.

The Kataphorite Group species containing magnesium (Mg) and with ferric iron (Fe³⁺) greater than aluminum (Al) in the C position was named Magnesio-Katophorite in the 1978 and 1997 IMA amphibole nomenclature. However, the Katophorite Group minerals were redefined in the 2012 IMA amphibole nomenclature. The 2012 change renamed the Mg, Fe³⁺ and (OH) dominant member of the group Ferri-Katophorite.

The mineral Katophorite was first described by W.C. Brøgger (1894) as an Amphibole mineral that he found at three localities in the Permian Oslo Region, Norway. The minerals originally designated by Brøgger (1894) as "Katophorite" are, according to the new Amphibole nomenclature, classified as Ferro-Katophorite. Katophorite, without any element modifiers, is the name given to an Amphibole occurance found in 2013 at the Hpakant-Tawmaw Jade Tract, Hpakant Township, Mohnyin District, Kachin State, northern Myanmar (Burma). Katophorite is named from the Greek word
κατώφορος (kataphora) meaning carrying down, in allusion to its volcanic origin.

Katophorite is typically black, dark greenish black or bluish black with vitreous luster and usually opaque but may also be transparent to translucent in thin slivers. Black Katophorite Is often found associated with greenish black Arfvedsonite, white Feldspar, and red Eudialyte at the Kipawa alkaline complex in Canada (see gem pictured above). This makes for a very unusual and attractive gem.

Distribution: may occur in the Oslo (Christiania) district, Norway, from where it was originally described. On the Rallier-du-Baty Peninsula, Kerguelen Island, in the south Indian Ocean. In the Kipawa alkaline complex, Les Lacs-du-Témiscamingue, Témiscamingue RCM, Abitibi-Témiscamingue, Québec, Canada. At the Hpakant-Tawmaw Jade Tract, Hpakant Township, Mohnyin District, Kachin State, northern Myanmar (Burma).
 

  
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