Often, people regard pearl as a gemstone, however, in reality, the pearl (Moti) is not a mineral in spite of that it is a composition of minerals called Aragonite and Conchiolin (which is an organic compound). In other words, we can say that pearl gemstone is the combination of calcium and protein. Thus, it is said that wearing pearl stone (Moti) strengthens the bones of the human being. - See more at: http://pearl.org.in/pearl-stone-a-composition-of-aragonite-and-conchiolin/