CSIRO sapphire homogeneity measurement
Two sapphire samples, A and B, provided by Caltech were measured on CSIRO’s Large Aperture Digital Interferometer (LADI) to determine optical homogeneity of the material in two orthogonal directions. The samples, which have an m-axis crystal orientation,  have a nominal diameter of 150 mm, a thickness of 80 mm and a wedge of around 1° on one face. The c-axis of the crystal structure appears to be oriented nominally parallel to the wedge direction. This was verified in a white light strain viewer where the sample is viewed between crossed polarisers.  Both sides of the samples, as supplied,  were polished to a surface figure better than a fringe.

Full Text of CSIRO measurement report and analysis(.pdf)
The following table is an excerpt from the full report by CSIRO (link above) .JPG images of the data.  Color scales are autoscaled to each data set
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  Filename/image Comments rms
(nm)		 Dn
(ppm)		  rms –T,P
(nm)		 rms -ATR
(nm)		 Data Format
1. saphah0a ^, S2(sup) 30.2 0.38 25.4  20.7 Raw Ascii Data  Restored Data
2. saphah0b ^, S1(sup) 28.9 0.36  24.2  20.4  
3. saphah9a //, S2(sup) 24.7 0.31  20.1  17.2 Raw Ascii Data  Restored Data
4. saphah9b //, S1(sup) 23.3 0.29  18.6  17.1  
5. saphah9c //, S1(sup) 24.1 0.30  20.0  17.2  
6. saphbh0a ^, S1(sup) 58.4 0.73  48.7  33.6 Raw Ascii Data   Restored Data
7. saphbh0b ^, S2(sup) 57.6 0.72  47.5  33.9  
8. saphbh9a //, S1(sup) 41.4 0.52 27.1  15.5 Raw Ascii Data  Restored Data
9. saphbh9b //, S2(sup) 41.1 0.51  26.4  15.8  
10. saphbh9c //, S1(sup) 42.3 0.53  27.9  15.5  
11. saphbt0a