Rare Minerals

Astrophyllite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_S25-Astrophyllit-5-OA_002b.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_S25-Astrophyllit-5_002b.jpg
Formula (K,Na)3(Fe2+,Mn)7Ti2Si8O24(O,OH)7
Crystal System triclinic
Mineral-Group Astrophyllite-Group
Colour golden yellow
Pleochroism strong, yellow to brown
Cleavage one
Twinning  -
Birefringence Δ = 0.009 - 0.020
Extinction  -
Optical Class 2 (+)
Special Features  -


 

Axinite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Axinit-20-OA-Spaltbarkeit_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Axinit-20-Spaltbarkeit_001.jpg
Formula Ca2(Fe,Mn,Mg)Al2BSi4O15(OH)
Crystal System triclinic
Mineral-Group Axinite-Group (Sorosilicate)
Colour colourless
Pleochroism only in thicker sections
Cleavage one to multiple (tot. four)
Twinning  -
Birefringence ∆ ≈ 0.010
Extinction inclined
Optical Class 2 (−)
Special Features zoning; anomalous IC
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Axinit-20_001b.jpg

 

Brucite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Brucit-10-OA_003.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Brucit-10_003.jpg
Formula Mg(OH)2
Crystal System hexagonal, trigonal
Mineral-Group Brucite-Group
Colour colourless
Pleochroism  -
Cleavage one
Twinning  -
Birefringence Δ = 0.009 - 0.020
Extinction  -
Optical Class 1 (+)
Special Features anomalously biaxial; forms coarse or layered to flaky aggregates; anomalous IC


 

Carpholite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_DEM2-2.5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_DEM2-2.5-OA_001.jpg
Formula (Mn,Mg,Fe)Al2Si2O6(OH)4
Crystal System orthorhombic
Mineral-Group Carpholite-Group (Px-related)
Colour pale yellow, pale brown
Pleochroism colourless to light brown
Cleavage one
Twinning  -
Birefringence Δ = 0.022
Extinction straight
Optical Class 2 (−)
Special Features  -
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_DEM2-2.5_001.jpg

 

Clinochlore

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_S4251-5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_S4251-5_001.jpg
Formula (Mg,Fe2+)5Al(Si3Al)O10(OH)8
Crystal System monoclinic
Mineral-Group Chlorite-Group
Colour green, yellow-green
Pleochroism  -
Cleavage one
Twinning lamellar
Birefringence Δ = 0.011
Extinction inclined
Optical Class 2 (+) / 2 (−)
Special Features  -
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_S4251-2.5-OA_001.jpg

 

Chloritoid

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Chloritoid-2.5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Chloritoid-2.5-OA_003.jpg
Formula (Fe,Mg)2Al4Si2O10(OH)4
Crystal System monoclinic, triclinic
Mineral-Group Chloritoid-Group (Nesosilicate)
Colour colourless to pale yellow, greyish green, slate blue
Pleochroism strong
Cleavage one (tot. three)
Twinning twins, triplets, polysynthetic twins
Birefringence ∆ ≈ 0.006 - 0.022
Extinction inclined (ε = 26°-32°)
Optical Class 2 (+) / 2 (−)
Special Features hour-glass (sector) zoning; anomalous IC
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Chloritoid-2.5_003.jpg

 

Deerite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Deerit-5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Deerit-5_003.jpg
Formula (Fe2+)12(Fe3+)6Si12O40(OH)10
Crystal System monoclinic
Mineral-Group Deerite-Group (Inosilicate)
Colour almost black
Pleochroism  -
Cleavage  -
Twinning  -
Birefringence Δ ≈ 0.030
Extinction  -
Optical Class 2
Special Features  -


 

Dumortierite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_BAT21-10-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_BAT21-10-OA_002.jpg
Formula Al7(BO3)(SiO4)3O3
Crystal System orthorhombic
Mineral-Group Borosilicate (Nesosilicate)
Colour blue
Pleochroism distinct, pale blue to light blue
Cleavage one (tot. three)
Twinning penetration triplets
Birefringence Δ ≈ 0.031
Extinction straight
Optical Class 2 (−) / 2 (+)
Special Features  -
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_BAT21-10_003.jpg

 

Høgtuvaite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Hoegtuvait-10-OA_003.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Hoegtuvait-10_003.jpg
Formula (Ca,Na)2(Fe2+,Fe3+,Ti)6
(Si,Be,Al)6O20
Crystsal System triclinic
Mineral-Group Aenigmatite-Group (Inosilicate)
Colour brown (alternatively opaque)
Pleochroism strong
Cleavage two (≈ 55°)
Twinning polysynthetic
Birefringence Δ ≈ 0.040
Extinction inclined (ε ≈ 13°-18°)
Optical Class 2 (−)
Special Features  -


 

Holmquistite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Holmquisit-2.5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Holmquisit-2.5_001.jpg
Formula (Li2Mg3Al2)Si8O22(OH)2
Crystal System orthorhombic
Mineral-Group Li-Mg-Amphibole
Colour colourless
Pleochroism  -
Cleavage two (≈ 124°/56°)
Twinning  -
Birefringence Δ = 0.033 - 0.041
Extinction straight
Optical Class 2 (−)
Special Features  -


 

Howieite

 

Formula Na(Fe2+,Mn)10(Fe,Al)2Si12(O,OH)44
Crystal System triclinic
Mineral-Group Howieite-Group (Inosilicate)
Colour green, beige
Pleochroism strong
Cleavage one (tot. three)
Twinning  -
Birefringence Δ ≈ 0.033
Extinction  -
Optical Class 2 (−)
Special Features  -




tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Howieit-5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Howieit-5-OA_002.jpg
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Howieit-5_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Howieit-5_003.jpg

 

Kaersutite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_IV4-2.5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_IV4-2.5-OA_002.jpg
Formula NaCa2Mg3Fe2+(Ti,Fe3+)[(OH)2|Al2Si6O22]
Crystal System monoclinic
Mineral-Group Amphibole (Titanium Hornblende)
Colour brown
Pleochroism distinct
Cleavage two (≈ 124°/56°)
Twinning lamellar
Birefringence Δ = 0.024 - 0.027
Extinction inclined (ε ≈ 3°-19°)
Optical Class 2 (−)
Special Features  -
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_IV4-2.5_001.jpg

 

Kornerupine

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Kornerupin(S90)-5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Kornerupin(S90)-5_002.jpg
Formula (Mg,Fe2+)4Al6(Si,Al,B)5O21(OH)
Crystal System orthorhombic
Mineral-Group Borosilicate (Sorosilicate)
Colour colourless, pale blue
Pleochroism very weak
Cleavage one
Twinning regular to multiple
Birefrigence Δ = 0.012
Extiction straight
Optical Class 2 (−)
Special Features pseudo-uniaxial
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Kornerupin(S90)-10_003.jpg

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Kornerupin(S90)-5-OA_003.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Kornerupin(S90)-5_001.jpg

 

Lazurite (Lapis Lazuli)

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Lazurit-5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Lazurit-5_002.jpg
Formula Na3Ca(AlSiO4)3(SO4,S2)
Crystal System cubic
Mineral-Group Sodalite-Group
Colour intense blue
Pleochroism  -
Cleavage one
Twinning  -
Birefringence  -
Extinction  -
Optical Class isotropic
Special Feature anomalously anisotropic


 

Nosean

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Nosean-10-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Nosean-10-_002.jpg
Formula Na8(AlSiO4)6(SO4)
Crystal System cubic
Mineral Group Sodalite-Group (Foid)
Colour colourless to grey brown
Pleochroism  -
Cleavage one (indistinct)
Twinning  -
Birefringence  -
Extinction  -
Optical Class isotropic
Special Features zonal accumulation (= segregated particles of iron ore)
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Noseanphonolith-10-OA_006.jpg

 

Piemontite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Piemontit-2.5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Piemontit-2.5_001.jpg
Formula Ca2Al2Mn3+SiO4Si2O7O(OH)2
Crystal System monoclinic
Mineral-Group Mn-bearing Epidote
Colour yellow, crimson, violet
Pleochroism very strong, from yellow to crimson
Cleavage two (≈ 115°)
Twinning regular to multiple
Birefringence Δ = 0.025 - 0.088
Extinction straight; inclined (ε ≈ 30°-37°)
Optical Class 2 (+) / 2 (−)
Special Features zoning
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Piemontit-10_002.jpg

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Piemontit-10-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Piemontit-10-OA_002.jpg

 

Pyrochlore

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Pyrochlor-10-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Pyrochlor-10-OA_001.jpg
Formula (Ca,Na)2Nb2O6(OH,F)
Crystal System cubic
Mineral-Group Pyrochlore-Group
Colour brown, red, yellow, colourless
Pleochroism  -
Cleavage  -
Twinning  -
Birefringence  -
Extinction  -
Optical Class isotropic
Special Features zoning
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Pyrochlor-10_003.jpg

 

Sapphire

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Saphir-5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Saphir-5_001.jpg
Formula Al2O3 with Fe, Ti
Crystal System trigonal, hexagonal
Mineral-Group Hematite-Group (Var. of Corundum)
Colour colourless, bluish
Pleochroism weak
Cleavage only partings
Twinning lamellar
Birefringence Δ = 0.008 - 0.009
Extinction straight
Optical Class 1 (−)
Special Features zoning; high relief; irregular colour distribution



tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Saphir-10-OA_004.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Saphir-10_001.jpg

 

Sapphirine

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sapphirin-2,5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sapphirin-2,5-OA_003.jpg
Formula (Al,Mg)8(Al,Si)6O20
Crystal System monoclinic
Mineral Group Sapphirine-Group (Inosilicate)
Color indigo-blue, brownish yellow
Pleochroism distinct
Cleavage three (poor/indistinct)
Twinning  -
Birefringence Δ = 0.005 - 0.007
Extinction inclined
Optical Class 2 (+) / 2 (−)
Special Features anomalous IC
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sapphirin-2,5_002.jpg

 

Sillimanite [cross-section]

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sillimanit(S90)-10-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sillimanit(S90)-10_002.jpg
Formula Al2SiO5
Crystal System orthorhombic
Mineral-Group Alumosilicate
Colour colourless
Pleochroism  -
Cleavage one (distinct)
Twinning  -
Birefringence ∆ = 0.019 - 0.022
Extinction straight
Optical Class 2 (+)
Special Features  -


 

Spodumene

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Spodumen-5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Spodumen-5_002.jpg
Formula LiAlSi2O6
Crystal System monoclinic
Mineral-Group Pyroxenes (Clinopyroxene)
Colour colourless
Pleochroism  -
Cleavage two (≈ 87°)
Twinning rare
Birefringence Δmax = 0.020
Extinction inclined (ε = 23°-27°)
Optical Class 2 (+)
Special Features  -



tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Spodumen-10-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Spodumen-10_001.jpg

 

Stilpnomelane

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Stilpnomelan-2.5-OA_003.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Stilpnomelan-2.5_0001.jpg
Formula K(Fe,Mg,Al)3Si4O10(O,OH)2·3H2O
Crytsal System monoclinic
Mineral-Group Phyllosilicate
Colour yellow, brown, greenish
Pleochroism strong
Cleavage one
Twinning  -
Birefringence Δ = 0.030 - 0.110
Extinction straight on cleavages
Optical Class 2 (−)
Special Features pseudouniaxial; in contrast to biotite without "birdseye"-structure
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Stilpnomelan-5_002.jpg

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Stilpnomelan-2.5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Stilpnomelan-2.5_001.jpg

 

Sugilite (Lavulite)

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sugilit-2.5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sugilit-2.5_002.jpg
Formula KNa2(Fe2+,Mn2+,Al)2Li3Si12O30
Crystal System hexagonal
Mineral-Group Milarite-/Osumilite-Group (Cyclosilicate)
Colour pink, yellow orange, reddish violet
Pleochroism weak (strong due to the thickness)
Cleavage indistinct (one)
Twinning  -
Birefringence Δ ≈ 0.003
Extinction  -
Optical Class 1 (−)
Special Features zoning
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sugilit-5-OA_001.jpg

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sugilit-5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Sugilit-5_004.jpg

note: section is thicker than usual

 

Titanite (Sphene)

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Titanit-10-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Titanit-10_001.jpg
Formula CaTiSiO4(OH,F)
Crystal System monoclinic
Mineral Group Titanite-Group (Nesosilicate)
Colour colourless, brownish yellow, greenish
Pleochroism distinct
Cleavage one (disitinct); one parting
Twinning regular
Birefringence Δ = 0.100 - 0.192
Extinction rhombic cuts: symmetrical (often incomplete)
otherwise: inclined (ε = 36-51°)
Optical Class 2 (+)
Special Features characteristic wedge shape; weak zoning; very high relief


 

Topaz

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Topas-5_OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Topas-5_003.jpg
Formula Al2SiO4(OH,F)2
Crystal System orthorhombic
Mineral Group Nesosilicate
Colour colourless
Pleochroism  -
Cleavage one (very good)
Twinning  -
Birefringence Δ = 0.008 - 0.011
Extinction straight
Optical Class 2 (+)
Special Features  -


note: section is thicker than usual

 

Tremolite (Grammatite)

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Tremolit-2,5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Tremolit-2,5_001.jpg
Formula Ca2Mg5Si8O22(OH)2
Crystal System monoclinic
Mineral Group Actinolite-series (Ca-Amphibole)
Colour colourless
Pleochroism  -
Cleavage two (≈ 124°/56°)
Twinning regular, rarely polysynthetic
Birefringence ∆ ≈ 0.022
Extinction inclined (ε ≈ 15°-20°)
Optical Class 2 (−)
Special Features  -
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Tremolit-2,5_002.jpg

 

Vesuvianite (Idiocrase)

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Vesuvian-5-OA_003.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Vesuvian-5_003.jpg
Formula Ca10(Mg,Fe)2Al4Si9O34(OH,F)4
Crystal System tetragonal
Mineral-Group Vesuvianite-Group (Sorosilicate)
Colour colourless, pale yellow / green / brown
Pleochroism weak
Cleavage poor (tot. three)
Twinning  -
Birefringence ∆ = 0.001 - 0.008
Extinction straight
Optical Class 1 (−) / 1 (+)
Special Features zoning; anomalous IC


 

Wollastonite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Wollastonit-2.5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Wollastonit-2.5_001.jpg
Formula Ca3(Si3O9)
Crystal System triclinic (pseudo-monoclinic), monoclinic
Mineral-Group Wollastonite-Group, Pseudopyroxene (Inosilicate)
Colour colourless
Pleochroism  -
Cleavage three (good)
Twinning lamellar
Birefringence ∆ = 0.013 - 0.014
Extinction inclined (ε = 3°-5°)
Optical Class 2 (−)
Special Features  -


 

Rare Earth Minerals

 

Bastnäsite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Bastnaesit-2.5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Bastnaesit-2.5_001.jpg
Formula (Ce,La,Y)(CO3)F
Crystal System hexagonal, trigonal
Mineral-Group Carbonate
Colour colourless, light brown
Pleochroism  -
Cleavage one (indistinct); one parting
Twinning  -
Birefringence Δ ≈ 0.100
Extinction straight, symmetrical
Optical Class  1 (+)
Special Features  -




tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Bastnaesit-2.5-OA_005.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Bastnaesit-2.5_004.jpg
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_BastnaesitEK-2.5-OA_003.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_BastnaesitEK-2.5_002.jpg

 

Eudialite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Eudialith-5-OA_004.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Eudialith-5_003.jpg
Formula Na15Ca6(Fe2+,Mn2+)3Zr3[Si25O73](O,OH,H2O)3(OH,Cl)2
Crystal System trigonal, hexagonal
Mineral-Group Eudialite-Group (Cyclosilicate)
Colour colourless
Pleochroism  -
Cleavage one (tot. two)
Twinning  -
Birefringence Δ ≈ 0.004
Extinction  -
Optical Class 1 (+) / 1 (−)
Special Features irregular distribution of the IC



tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Schneemann(Eudialith)-5-OA_001 copy.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Eudialith-5_001.jpg

 

Gadolinite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Gadolinit-5-OA_002.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Gadolinit-5-OA_001.jpg
Formula (Ce,La,Nd,Y)2Fe2+Be2Si2O10
Crystal System monoclinic
Mineral-Group Gadolinite-Group (Nesosilicate)
Colour beige-maroon, olive
Pleochroism distinct (only in thicker sections)
Cleavage one
Twinning  -
Birefringence ∆ ≈ 0.024
Extinction inclined (ε = 2°-12°)
Optical Class 2 (+)
Speacial Features  -
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Gadolinit2-5_002.jpg

 

Koppite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Koppit-10-OA_005.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Koppit-10_005.jpg
Formula (Na,Ca)2(Nb,Ti,Ta,Y)2O6(OH,F)
Crystal System cubic
Mineral-Group Pyrochlore-Group (Oxide)
Colour brown, red
Pleochroism  -
Cleavage  -
Twinning  -
Birefringence  -
Extinction  -
Optical Class  isotropic
Special Features zoning


 

Loparite

 

tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Loparit(5222)-5-OA_001.jpg tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Loparit-5_002.jpg
Formula (Ce,Na,Ca)(Ti,Nb)O3
Crystal System cubic
Mineral-Group Perowskite-Group (Oxide)
Colour purple-brown, yellow-brown
Pleochroism weak
Cleavage one
Twinning penetration twins
Birefringence  -
Extinction  -
Optical Class isotropic
Special Features anomalously anisotropic
tl_files/arbeitsgruppen/ag_mineralogie/Seltene_Minerale/w_Loparit(5222)-10-OA-Farbverteilung_001.jpg

 

Information

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© by Barbara Bsdok & Anne Zitzmann