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| Formula | (Ca,Na)(Mg,Fe2+,Fe3+,Al)Si2O6 |
| | Optic class & sign | Biaxial positive |
| | Optical orientation | a near X, b = Y, c at a high angle to Z |
| | Optical plane | (010) |
| | Relief | High |
| | Refractive indices | nx = 1.662 -1.701
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ny = 1.670 -1.712
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nz = 1.685 -1.723
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| n decreases with increasing jadeite component along the Jd-Di join; increases with increasing Aeg component |
| | Birefringence (max.) | 0.012 - 0.028 |
| | | Δn decreases with increasing jadeite component along the Jd-Di join; increases with increasing Aeg component |
| | Optic Angle
| 2Vx
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| | 2Vz
= 56 - 84° |
| | Sign of elongation | Due to large angle between c and Z, not readily applicable |
| | Interference figure | Large 2V isogyres with few isochromes |
| | Colour / pleochroism | Colourless to pale green, weakly pleochroic; absorption Y = Z > X |
| | Zoning | |
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| Form | Habit | Granular |
| | | Surface | Commonly anhedral |
| | Cleavage | 2 sets {110} distinct, at 93 and 87° (seen in sections ⊥ c); in prismatic sections, the traces of the two principal cleavage sets are parallel. |
| | Twinning | Simple or multiple on {100} and {001} |
| | Extinction | Inclined, cɅZ = 36 - 48° in (010) sections; c ∥ cleavage traces and prism faces. Symmetrical extinction to {110} cleavage in sections ⊥ c. |
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| Reaction textures | Replacement by Na- or Ca-amphiboles |
| | Alteration / decomposition | |
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| Occurence | Ign | |
| | | Met | Eclogite, less common in blueschists |
| | | Sed | |
| | | Hyd | |
| | | Other | |
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| Distinctive properties | Moderate Δn, large extinction angles in maximum birefringence sections, characteristic pyroxene cleavage observed in sections ⊥ c. Restricted occurrence, in paragenesis with abundant garnet. |
| | Additional comments | |
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