Antique porcelain was initially interchangeable with gold and jewels as a symbol of wealth, especially in medieval Europe. Originally developed in tenth-century China (hence the other name for porcelain being "china"), porcelain is another type of pottery, composed of extremely white clay that is fired at a very high temperature and often applying a feldspathic glaze.  Italian explorer Marco Polo first brought back antique porcelain from the Orient from his travels to China in 1260. The well-guarded Chinese secret of producing antique porcelain eluded European craftsmen for another 450 years until Johannes Friedrich Böttger stumbled upon the correct formula as a sideline to his attempts to discover the "Philosopher's Stone", a since-proved bogus theory of converting base metal into gold. Under intense pressure from the Saxon King Augustus the Strong, Böttger learned that a key ingredient of antique porcelain was the mineral kaolin. Luckily there existed a rich supply not far from his base at the castle in Meissen. Antique porcelain is just another form of pottery. Pottery-making had been pursued wordwide since prehistoric times.  It was the Chinese, however, that first discovered the secret to its production, centuries before the inhabitants of Europe. An abundance of pottery fragments have been found in China, dating back to the Neolithic age.  These include plates and bowls along with figurines.  Starting with clay-strip pieces fired in the ground, the process eventually developed into the more precise throw-clay method, whose products were finished in side-fired and shaft kilns.  These innovations in technology, alongside increasing knowledge of atmospheric controls, allowed the early Chinese potters to fire their pieces at temperatures up to 1100 degrees.  This was very close to the critical temperature that separates pottery from porcelain. By the early Yin and Shang Dynasty, potters began using kaolin-an extremely white clay that can only be found in a few places in the world.  At this time, they also developed specialized kilns that could fire at 1200 degrees required to harden clay into an extremely hard, nonporous consistency.  Once these two necessary components were acquired, the invention of porcelain became virtually inevitable.  The first piece of true porcelain, however, was probably not produced until the Tang Dynasty (618-907). The art of porcelain production was mastered by the Ming Dynasty (1368-1644), and it was during this time that the first pieces of "china" began to be exported to Japan and Europe.  These pieces were highly valuable, and were praised by the likes of Marco Polo and Francis Bacon.  By this point, the Chinese were producing porcelain from two types of earth: the white clay kaolin, and a feldspathic stone called petuntse, which gave the final product a translucent, glasslike appearance.  The most complicated problem that arose during this time period was decoration, for the Chinese were only able to develop two colors that could withstand the high temperatures of the firing process-cobalt blue and copper red.  They also experimented with coloring the glaze itself, resulting in a subtle green or grey tint as found in the "celadon" pieces from the Tang Dynasty.  By far the most successful technique was the overglaze paint, which was applied to the outer surface after the first firing, and then fused to the glaze by a second firing at a lower temperature.  Using this method, they were able to produce virtually any color imaginable in the most intricate designs. After the beginnings of true hard-paste antique porcelain production in the early eighteenth century in Meissen, it was only a matter of time before the secret spread. New antique porcelain production srung up in such places as Dresden, Sevres, Limoges, Capodimonte, and variation such as bone china and ironstone china in such English manufactoies as Spode, Royal Doulton, and Wedgewood. Neither was the rest of Asia lying dormant. Japan has since produced masterful antique porcelain known as Nippon and Noritake. Finally, the art of porcelain production found its way to the New World via David Haviland and his sons. Haviland established a porcelain factory at Limoges, France, in the first half of the nineteenth century. Later, his family removed production to The United States.