Around 4,800 BIA a group of a several hundred Dwarves led by Torthil Grunnindaughter followed reports of a rich copper deposit somewhere deep in the Southern Continent's Great Desert which desert nomads occasionally mined when passing through. Eventually they found such a sight in dry foothills and established a small settlement. Life was difficult in an area which received an average of two centimeters of rain, even after they carved out their homes into the dry rock. Their numbers got a boost during the War of Four Centuries as Dwarven refugees fled south in search of safety, which resulted in a boost in population and several more settlements being established to bolster their population. The adaptations that they developed to survive in this barren wasteland were fairly remarkable, from refinements to traditional Dwarven Agriculture
to the creation of cisterns, aqueducts and condensers to supply water. Even so these settlements remained fairly small with maybe ten thousand members each, trading with herders and caravaniers for food and supplies. For several thousand years they remained marginal. Their holds never had more than fifteen thousand people each and even today their total population is still only about 300,000 of them. Never the less they survived and created a distinctive highly thrifty culture: the Sand Dwarves.
Then around 1,100 BIA one of their artisans came up with a solution to a problem that his/her hold faced: the matter of fuel. While some Sand Dwarf holds had access to some reasonable deposits of coal many did not. Trading for coal was difficult at the best of times, wood was rare and often they were reduced to burning dung charcoal. To get around this they began to use mirrors to focus sunlight on a specific point. First for cooking and latter for processing ore, using a small amount of coal or charcoal in the process as a reducing agent. As time went on their designs were soon duplicated by other Sand Dwarf holds (who developed this first is a contested matter) and the designs refined and enlarged, especially as they were used to make more and better mirrors. Now across the equatorial region there are hundreds of solar furnaces, ranging in sophistication to dishes in craters to adjustable affairs using counterweights and pivots to better track the sun, focusing it into a ceramic furnace which can reach temperatures of up to 3,000 degrees. Slag is removed and liquid metal is collected at sundown to be either further worked or stored.
Among the more notable aspects of using these mechanisms for smelting was discovered after the fact, iron smelted in such a fashion has a certain degree of magic infused to it. The effects of this in most cases is minimal in the case of material that had simply been smelted, but several days of heating and re-heating in a furnace can produce metal which is easy for runesmiths to ply their craft on. Using said material they can forge three runic swords in the time it takes to make two of said swords from regular iron. Only meteoric iron is comparable. Ingots of repeatedly solar smelted iron can fetch up to ten times the value of regular iron ingots. Being an equatorial region that rarely sees cloud cover, solar smelting is a profitable venture for the Sand Dwarves, as does the use of mirrors which were made in solar furnaces by Dwarves who've refined their craft in that field for maximum mana reflectively over centuries who guard their secrets tightly. Attempts to replicate the process have, as of 37 IA, been uneconomical.