So, the quality of mirror would consist of uniquely reflected light. The orient, on the other hand, would be due to light comming into the pearl, getting distorted by the floating layers/sheets of aragonite crystals and comming out refracted as if through a prism(thus the rainbow effect). The thinner the sheets of suspended aragonite crystals, the better the orient. The more of these thin suspended aragonite sheets, the better the orient.

Sometimes one can see the multiple thin concentric sheets of aragonite very easily. Between these aragonite sheets there is another colourless, translucent sheet of various thickness. What is this translucent sheet? Is it conchiolin? Or is it just a trick of light? There should be very little conchiolin compared to aragonite.

Slraep