<P> Thin transparent sheets of mica were used for peepholes in boilers, lanterns, stoves, and kerosene heaters because they were less likely to shatter than glass when exposed to extreme temperature gradients . Such peepholes were also used in "isinglass curtains" in horse - drawn carriages and early 20th century cars . </P> <P> Another use of mica is as a substrate in the production of ultraflat, thin - film surfaces, e.g. gold surfaces . Although the deposited film surface is still rough due to deposition kinetics, the back side of the film at the mica - film interface is ultraflat once the film is removed from the substrate . Freshly - cleaved mica surfaces have been used as clean imaging substrates in atomic force microscopy, enabling for example the imaging of bismuth films, plasma glycoproteins, membrane bilayers, and DNA molecules . </P> <P> Human use of mica dates back to prehistoric times . Mica was known to ancient Indian, Egyptian, Greek and Roman and Chinese civilizations, as well as the Aztec civilization of the New World . </P> <P> The earliest use of mica has been found in cave paintings created during the Upper Paleolithic period (40,000 BC to 10,000 BC). The first hues were red (iron oxide, hematite, or red ochre) and black (manganese dioxide, pyrolusite), though black from juniper or pine carbons has also been discovered . White from kaolin or mica was used occasionally . </P>

Which of the following is the main area for mica production