Note that the Orientation Slice is cut precisely to the (100) before the crystal is rotated and cut at either +.25 degrees and toward the flat, or â.25 degrees and away from the flat (as described in Figure 3).
The era was called the Dark Ages also because we don't have a lot of written sources from that time period, especially from the early part of the dark ages (500 to 800 CE).
Why is it called the Dark Ages ? The period, generally after the fall of the Western Roman Empire until, the 1000s I should say, has often been described as a Dark Age for Europe (It was golden age to us ).