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Chegemite

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Formula:
Ca7(SiO4)3(OH)2
System:
Orthorhombic
Colour:
pink, yellow-pink to ...
Hardness:
5½ - 6
Name:
from the Chegem River where the new mineral was discovered in the headwater tributary-area
Ca- and OH-dominant analogue of Humite.
OH-analogue of Unnamed (F-analogue of Chegemite).


Classification of Chegemite

Approved
Approval Year:
2008

Type Occurrence of Chegemite

General Appearance of Type Material:
granular aggregates with grain sizes up to 5 mm
Place of Conservation of Type Material:
Fersman Mineralogical Museum in Moscow, Russia, with the number 3731/1 and the single grain used for structural investigation is deposited in the Museum of Natural History in Bern, Switzerland, with the number NMBE 39571.
Geological Setting of Type Material:
a rock-forming mineral in high-temperature skarns (sanadinite) in calcareous xenoliths in ignimbrites

Physical Properties of Chegemite

Colour:
pink, yellow-pink to white.
Streak:
white
Hardness (Mohs):
5½ - 6
Hardness (Vickers):
VHN100=315
Cleavage:
Imperfect/Fair
(010)
Fracture:
Conchoidal
Density:
2.86(1) g/cm3 (Measured)    2.892 g/cm3 (Calculated)

Crystallography of Chegemite

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:
a = 5.0696(1) Å, b = 11.3955(1) Å, c = 23.557(3) Å
Ratio:
a:b:c = 0.445 : 1 : 2.067
Unit Cell Volume:
V 1360.91 ų
Z:
4
Twinning:
Twins, probably on (110)
Comment:
space group Pbnm
X-Ray Powder Diffraction Data:
d-spacingIntensity
5.611 (43)
3.646 (41)
3.041 (65)
2.837 (60)
2.728 (74)
2.557 (43)
2.520 (59)
1.910 (100)

Optical Data of Chegemite

Type:
Biaxial
RI values:
nα = 1.621(2) nβ = 1.626(3) nγ = 1.630(2)
Birefringence:
Max Birefringence:
δ = 0.009
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate

Chemical Properties of Chegemite

Formula:
Ca7(SiO4)3(OH)2
Elements listed in formula:

Relationship of Chegemite to other Species

Series:
Forms a series with Fluorchegemite (see here)
Other Members of Group:
EdgrewiteCa9(SiO4)4F2
KumtyubeiteCa5(SiO4)2F2
ReinhardbraunsiteCa5(SiO4)2(OH,F)2

Other Names for Chegemite

Name in Other Languages:

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Chegemite

Reference List:
Galuskin, E. V.; Gazeev, V. M.; Lazic, B.; Armbruster, T.; Galuskina, I. O.; Zadov, A. E.; Pertsev, N. N.; Wrzalik, R.; Dzierzanowski, P.; Gurbanov, A. G. & Bzowska, G. (2009): Chegemite Ca7(SiO4)3(OH)2 - a new humite-group calcium mineral from the Northern Caucasus, Kabardino-Balkaria, Russia. European Journal of Mineralogy 21, 1045-1059.

Internet Links for Chegemite

mindat.org URL:
http://www.mindat.org/min-39004.html
Please feel free to link to this page.
Specimens:
The following Chegemite specimens are currently listed for sale on minfind.com.

Localities for Chegemite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Russia
 
  • Northern Caucasus Region
    • Kabardino-Balkarian Republic
      • Baksan Valley
Galuskin, E.V., Galuskina, I.O., Kusz, J., Gfeller, F., Armbruster, T., Bailau, R., Dulski, M., Gazeev, V.M., Pertsev, N.N., Zadov, A.E., Dzieržanowski, P. (2015): Mayenite supergroup, part II: Chlorkyuygenite from Upper Chegem, northern Caucasus Kabardino-Balkaria, Russia, a new microporous mayenite supergroup mineral with “zeolitic” H2O. European Journal of Mineralogy. 27, 113-122; Bailau, R., Gałuskin, E. V., Gazeev, V. M., & Gałuskina, I. O. Raman investigation of potential new mineral-Fe 3-analogue of wadalite from calcareous-silicate xenoliths of the Upper Chegem caldera, Northern Caucasus, Russia.
          • Lakargi Mt.
Galuskin, E. V.; Gazeev, V. M.; Lazic, B.; Armbruster, T.; Galuskina, I. O.; Zadov, A. E.; Pertsev, N. N.; Wrzalik, R.; Dzierzanowski, P.; Gurbanov, A. G. & Bzowska, G. (2009): Chegemite Ca7(SiO4)3(OH)2 - a new humite-group calcium mineral from the Northern Caucasus, Kabardino-Balkaria, Russia. European Journal of Mineralogy 21, 1045-1059.
Galuskin, E. V.; Gazeev, V. M.; Lazic, B.; Armbruster, T.; Galuskina, I. O.; Zadov, A. E.; Pertsev, N. N.; Wrzalik, R.; Dzierzanowski, P.; Gurbanov, A. G. & Bzowska, G. (2009): Chegemite Ca7(SiO4)3(OH)2 - a new humite-group calcium mineral from the Northern Caucasus, Kabardino-Balkaria, Russia. European Journal of Mineralogy 21, 1045-1059.
Mineral and/or Locality  
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