Today 99% of the people we see using pearls are actually using CULTURED- pearls. These cultured-pearls are considered to have little astrological (Moon) influence, if any, because the main body of the so-called pearl is NOT PEARL, but some pre-formed shell-ball implant. That means it is not a natural complete unit, but just a thin covering of real pearl substance (called nacre) on the surface of a pre-shaped and pre-sized non-pearl bead. A cultured-pearl contains only a small percentage of pearl, most of the body is NOT PEARL.
In ancient Oriental and European histories we know that the "Pearl" they referred to was 100% natural pearl, because cultured-pearls were not known until recently. But at the present time practically everyone (except a learned gemologist) now thinks that the hollow "cultured pearl" pearl-imitations are the real thing. This is mass ignorance, and should be addressed by all cultured persons who care about the true nature of things.
Natural pearls are 100% 'pearl' or nacre. It is thought that natural pearls form under a set of accidental conditions when a microscopic intruder or grain of sand enters an oyster (mollusk) and settles inside the shell. The oyster, being irritated by the intruder, secretes the pearl substance called nacre to cover the irritant. This process is repeated for many years, thus producing a real pearl which may (or may not) be found by man. For a natural pearl to form with a nice round or oval shape, and be free of any flaws, is actually a real-life "miracle." The odds of a perfect natural pearl are 1 in a million.
Think about your knowledge of pearls... Did you know that 'cultured' pearls (nucleated and non-nucleated or tissue nucleated cultured pearls) and imitation pearls can be distinguished from natural pearls by X-ray examination? Nucleated cultured pearls are often 'pre-formed' as they tend to follow the shape of the implanted shell bead nucleus. Once the pre-formed beads are inserted into the oyster, it secretes a few layers of nacre around the outside surface of the implant before it is removed after six months or more. When you X-ray a nucleated cultured 'so-called' pearl it will reveal a different structure to that of a natural pearl (solid center with no concentric growth rings, compared to a solid center with growth rings). Many nucleated cultured pearls used in the trade today are in fact mostly shell bead nuclei with very thin to thin nacreous coatings over them. A natural pearl however is solid nacre or 100% pearl.
Any well equipped internationally recognized gem testing laboratory such as the GIA's Gem Trade Laboratory or the new AGTA Gem Lab (under super-vision of noted pearl expert, Kenneth Scarratt) is able to separate natural pearls from their counterparts viz., cultured pearls, non-nucleated cultured pearls and imitation 'pearls'.