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).
In modern times, the term Dark Ages is still used in popular culture. Petrarch's ideological campaign to paint the Middle Ages in a negative light worked so well that Dark Ages is still in popular use nearly seven hundred years later.