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The critical resolved shear stresses (CRSSs) of hematite crystals were determined in compression tests for r-twinning, c-twinning and {a}-slip in the temperature range 25°C to 400°C, at 400 MPa confining pressure, and a strain rate of 10 -5 s -1 by Hennig-Michaeli and Siemes, 1982. In the present contribution newly performed experiments on hematite single crystals at temperatures up to 800°C at strain rates of 10 -5 s -1 and 300 MPa confining pressure extends the knowledge about the CRSS of twin and slip modes. Optical observations, neutron diffraction goniometry, SEM forescatter electron images and electron backscatter diffraction are applied in order to identify the glide modes. Both twinning systems and {a}-slip were confirmed by these methods. Besides the known glide systems the existence of the (c)-slip system could be stated. Mechanical data establish that the CRSS of r-twinning decreases from 140 MPa at 25°C to ~5 MPa at 800°C and for {a}-slip from >560 MPa at 25°C to ~40 MPa at 700°C. At room temperature the CRSS for c-twinning is around 90 MPa and at 600°C ~60 MPa. The data indicate that the CRSSs above 200°C seem to be between the values for rtwinning and {a}-slip. For (c)-slip only the CRSS at 600°C could be evaluated to ~60 MPa. Exact values are difficult to determine because other glide systems are always simultaneously activated.

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The low-and high-field magnetic anisotropy (AMS, HFA) of the Rhenohercynian mudstones and greywackes is compared to the theoretical anisotropy calculated from neutron texture goniometry measurements. The magnetic anisotropy is predominantly carried by the paramagnetic phyllosilicates in the form of chlorite/mica stacks and the ferromagnetic contribution is insignificant. The respective principal directions of the theoretical anisotropy and the AMS and HFA are sub-parallel; magnetic foliation reflects the orientation of the maximal concentration of phyllosilicate basal planes, magnetic lineation is subparallel to the intersection axis of those planes. For the purpose of quantitative comparison, the infrequently used standard deviatoric susceptibility as a measure of the HFA degree is employed. A very good linear correlation of the degree of theoretical anisotropy and the measured AMS and HFA is found. The prolate and oblate shapes of the respective fabric ellipsoids are reasonably well correlated. Neutron texture goniometry justifies the use of the conventional magnetic anisotropy technique for the assessment of the mineral fabric of studied rocks. When compared with other works relating the magnetic anisotropy to the mineral preferred orientation (examined by e.g. U-stage or X-ray texture goniometry) neutron texture goniometry seems to be a preferable and very precise method fabric analysis.