iron implements were made in Central Anatolia in very limited quantities around 1800 BCE and were in general use by elites, though not by commoners, during the New Hittite Empire (∼1400–1200 BCE). Archaeologists have found indications of iron working in Ancient Egypt, somewhere between the Third Intermediate Period and 23rd Dynasty (ca. 1100–750 BCE). Significantly though, they have found no evidence of iron ore smelting in any (pre-modern) period. In addition, very early instances of carbon steel were in production around 2000 years ago (around the first-century CE.) in northwest Tanzania, based on complex preheating principles. These discoveries are significant for the history of metallurgy. Most early processes in Europe and Africa involved smelting iron ore in a bloomery, where the temperature is kept low enough so that the iron does not melt. This produces a spongy mass of iron called a bloom, which then must be consolidated with a hammer to produce wrought iron. The earliest evidence to date for the bloomery smelting of iron is found at Tell Hammeh, Jordan (), and dates to 930 BCE (C14 dating). Later iron smelting From the medieval period, an indirect process began to replace the direct reduction in bloomeries. This used a blast furnace to make pig iron, which then had to undergo a further process to make forgeable bar iron. Processes for the second stage include fining in a finery forge. In the 13th century duringHigh Middle Ages the blast furnace was introduced by China who had been using it since as early as 200 b.c during the Qin dynasty. Puddling was also Introduced in the Industrial Revolution. Both processes are now obsolete, and wrought iron is now rarely made. Instead, mild steel is produced from a Bessemer converter or by other means including smelting reduction processes such as the Corex Process. Base metals The ores of base metals are often sulfides. In recent centuries, reverberatory furnaces have been used to keep the charge being smelted separately from the fuel. Traditionally, they were used for the first step of smelting: forming two liquids, one an oxide slag containing most of the impurities, and the other a sulfide matte containing the valuable metal sulfide and some impurities. Such "reverb" furnaces are today about 40 meters long, 3 meters high, and 10 meters wide. Fuel is burned at one end to melt the dry sulfide concentrates (usually after partial roasting) which are