Parachrysotile
A structural variant of Chrysotile
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Formula:
Mg3(Si2O5)(OH)4
Hardness:
2½ - 3
Crystal System:
Orthorhombic
Name:
Named in 1956 by Eric James William Whittaker from the Greek παρα "para" = beyond and chrysotile for its relationship to the root name mineral.
Unique Identifiers
Mindat ID:
3083
Long-form identifier:
mindat:1:1:3083:6
IMA Classification of Parachrysotile
Discredited
Classification of Parachrysotile
14.4.7
14 : Silicates not Containing Aluminum
4 : Silicates of Mg
14 : Silicates not Containing Aluminum
4 : Silicates of Mg
Physical Properties of Parachrysotile
Hardness:
2½ - 3 on Mohs scale
Optical Data of Parachrysotile
Type:
Biaxial (-)
RI values:
nα = 1.545 - 1.569 nβ = 1.546 - 1.569 nγ = 1.553 - 1.571
2V:
Measured: 20° to 60°
Max. Birefringence:
δ = 0.002 - 0.008
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Low (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
relatively weak
Chemistry of Parachrysotile
Mindat Formula:
Mg3(Si2O5)(OH)4
Element Weights:
Elements listed:
Crystallography of Parachrysotile
Crystal System:
Orthorhombic
Cell Parameters:
a = 5.3 Å, b = 9.24 Å, c = 14.71 Å
Ratio:
a:b:c = 0.574 : 1 : 1.592
Unit Cell V:
720.38 ų (Calculated from Unit Cell)
Z:
4
Other Language Names for Parachrysotile
German:Parachrysotil
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.
Internet Links for Parachrysotile
mindat.org URL:
https://www.mindat.org/min-3083.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Parachrysotile
Localities for Parachrysotile
Showing 5 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Eswatini | |
| Yada (1979) |
Germany | |
| Wittern (2001) |
South Africa | |
| Cairncross et al. (1995) |
USA | |
| Castor et al. (2004) |
Zimbabwe | |
| Mineralogical Society of America - ... |
