by Eric Flint
* * *
Commercially, mica is classified according to its thickness, size and appearance. (Paramount; Rouse, 340–1)
The term "block mica" tends to refer to large, thick pieces (at least 7 mils, one mil is one-thousand of an inch) which can be split and trimmed into useable sheets.
Sheet mica is at least 1 1/2 by 2 inches in size, and thinner (say, 1–7 mils) than a block. The thinner sheets, if of high quality, are sometimes referred to as "film."
The term "splittings" refers to pieces which are smaller than the smallest standard sheet, but at least 0.75 square inches in area. They are usually thin, too, perhaps 1–2 mils. Below that size we have waste or scrap mica, sometimes divided into flake mica and mica powder.
It is possible to assemble splittings into what is called "built-up" mica. Also, mica flakes and powder can be be used to make "reconstituted" mica ("micanite").
Micanite was invented in 1892 (Rajgartha, 4). Micanite is described in EB1911 as consisting of "small sheets of mica cemented with shellac or other insulating cement on cloth or paper." That is probably a sufficient description for the up-timers to duplicate it, if need be.
Paramount says that "the dielectric material used in the production of mica paper capacitors is reconstituted mica paper that is impregnated with a polymer resin." Nonetheless, the preferred material for capacitor dielectrics is certainly sheet mica. Chowdhury (257) says that "the highest quality mica, absolutely flawless, is required for radio and wireless purposes." (See also Rouse, 343). And Rouse (376) says that "the power loss shown by the bentonite films [for built-up mica] . . . is too high for them to be used in condensers . . ."
* * *
The quality rating of mica seems to have gone through many changes. Depending on which references you consult, there are anywhere from twelve to twenty possible rankings. The ASTM presently uses twelve (V-1 to V-7, V-7A, then V-8 to V-10A), which range from "clear" to "densely black and red stained. " I would expect, based on another source, that only V-1, V-2 ("clear and slightly stained"), V-3 ("fair stained") and V-4 ("good stained") are considered "capacitor grade. " (Misc. Diel.)http://my.execpc.com/~endlr/misc__dielectrics.html
We may be less picky in 1632, of course. Especially for receiver capacitors (USGS). The lesser grades of mica can, of course, be used as insulators, and that is a major use of micanite.
Mica Sources Reported in USE Reference Materials
As is too often the case for raw materials needed by the USE, the best known, most prolific sources of sheet mica are far away. We may have to pass through enemy spheres of influence to reach them; they may even be under enemy control.
So where do the encyclopedias direct us? EB1911 "Mica" says that muscovite sheets are found in India, the United States (South Dakota, Colorado and Alabama), and Brazil (Goyas, Bahia and Minas Gerais), and phlogopite in Canada and Ceylon.
The other Grantville encyclopedias don't distinguish between muscovite and phlogopite. The sources they list are:
Encyclopedia Americana: India, Madagascar, Brazil, USA (New Hampshire, North Carolina, South Dakota)
World Book Encyclopedia: India, Brazil, Madagascar, USA (North Carolina, New Mexico, South Dakota)
Modern Encyclopedia Britannica: India, South Africa, Soviet Union, Brazil, Argentina, Canada, Madagascar, USA (North Carolina, Idaho, South Dakota)
Collier's Encyclopedia notes that "the United States is the largest producer of bulk mica, but the greater part of the capacitor grade mica is mined in India." It adds that two-thirds of the American production was mined in North Carolina.
The encyclopedias provide no quantitative information. However, for the sake of the story writers, I will give a few numbers. The leaders in sheet mica production in the period 1913–1937, ignoring the secretive Soviet Union, were India (236,916,000 pounds, 74.6% of world production), United States (10.1%), Canada (4.8%), Madagascar (3.6%), Argentina (3.5%), Brazil (1.9%), and Rhodesia (1.4%). (Rouse, 349) In 2000, the largest producers were India (3,500 metric tons) and Russia (1,500)(USGS).
* * *
Prospectors are not, of course, limited to the known mica locations. However, without some kind of lead, the discovery of mica will be quite chancy.
Russian Mica
Russia, of course, has mica: the term "muscovite" is something of a giveaway. According to the Oxford English Dictionary, the term "Muscovy glass" was used in English to denote sheet mica at least as early as 1573. In 1604, J. Marston made reference to the ease with which thin sheets could be split off a mica "book" ("She were an excellent Lady, but that her face peeleth like Muscovy glass.") Hooke's Micrographica (1665) refers to the unusual optical properties of thin sheets of "Muscovy glass" (sheet mica from Russia).
What practical use was made of it? Mica sheets could serve as the clear but heat resistant panes of a lantern. T. Dekker, in 1606, referred to "a candle in a Muscovy lanthorn." They could also be used in more conventional windows. K. Digby noted in 1644 that the windows of his cabin were made of Muscovy glass.
It is clear from the foregoing that, by 1632, mica had been discovered in Russia, and exported to other countries. I don't have any economic data for the early seventeenth century, but in 1681, Russia exported 92,882 pounds of mica to Holland, 86,400 to England, and 18,000 to North America. (Chowdhury, 178). I have no idea what percentage of this was sheet mica, but the most likely use of the mica was in windows, and that would have required transparent (or translucent) sheets.
The Russians used it mostly as an "upscale" window material. In the late 1660s, Tsar Alexei Mikhailovitch had a summer palace built at Kolomenskoe, near Moscow. It had 3,000 mica windows.
Where does the Russian mica come from? The Hammond Citation World Atlas, which most likely made it through the RoF, contains an economic map of Russia and, lo and behold, identifies mica localities. I pity whoever goes to the Atlas' European Russian site; it is a little west of the far northern town of Kandalaksha, in Karelia. There are four mica localities shown to exist in Asiatic Russia, two of which are in the general vicinity of Irkutsk.
Fortunately, we don't have to find the mica ourselves, we just have to trade for it.
Indian (and Ceylonese) Mica
The encyclopedias consider India to be the premiere world source of muscovite sheet mica, so it is reasonable to consider it more closely.
According to Brown (541), "the date of the commencement of mica mining in India is lost in antiquity." However, it is unclear which of the current mica fields were known in the early seventeenth century.
Of course, we can give our Indian trading contacts some hint as to where to look, if need be. EB1911 says that mica is mined in Haziribagh (Bengal) and Nellore (Madras), and a prominent Nellore mine is "Inikurti."
I have also studied the economic map of India in the Hammond Citation World Atlas. To avoid inadvertent bias, I compiled my list of mica localities from the Atlas before examining even the encyclopedias, let alone any of the professional geological texts. I would estimate that the Atlas can be used to localize mica sites with an accuracy of perhaps 25–50 miles. The greatest is in Bihar, close to Hazaribagh. A second is also in Bihar, at the same longitude as Asansol, but north of the Ganges River. Monghyr, on the south bank, is nearby. The third is in Andhra Pradesh, near Nellore. That is all that the up-timers will know.
The USGS says that in India, "mica mines are operated in the States of Bihar, Andhra Pradesh, and Rajasthan. In Rajasthan, the principal mines are at Banjari, Barla, Bhojpura, Chapi, Galwa, Ganeshpur, Ghegas, Laxmi, and Sidiras. " An Indian government report says, "the main mica-sites in Andhra Pradesh are found at Atmakur, Ravuru and Gudur of Nellore district. Large deposits of Mica are also found at Tiruvuru in Krishna District, Madhira [Khammam District], and Ankannagudem of West Godavari, all in AP. " (MMPIndia)
* * *
The importation of mica sheets from India will be much easier if, by the early seventeenth century, it was already an article of commerce, something our traders could just ask
for. Gathering information on this issue has been something of an exercise in frustration.
Mica (Hindustani abrak, from abr cloud or abru the heavens) was used in ancient Indian medicine. The medical use of mica was probably of mica powder. Those who sell the medicines, or even the powders, may not know how to obtain the mica sheets. So it would be better to identify trade goods in which the mica sheets are used in intact form.
The mineral supposedly has been employed "from time immemorial, for ornaments, decorations and glazing, as well as by artists for their transparent paintings. It finds a place in the tinsel decorations of banners, taziahs and umbrellas at festivals and weddings. Its powder is sprinkled on clothes, fans and toys, as well as being incorporated in the glazes of some forms of pottery. . . ." (Brown, 541). Chowdhury (6) says that the "early" use of mica was in medicines, ornaments and vestries for idols, decorating, glazing or transparent mediums, and as a painting base (ground).
Like Brown and Chowdhury, EB1911 notes that sheets of mica have been used in India as a surface for painting. However, I believe that this began only after India came under British rule. (Swaveda, Chennai). A computer search in the Minassian Collection of Persian, Mughal and Indian Miniature Paintings turned up six mica paintings, all of which were dated as "Company School." Likewise, Swallow, Arts of India: 1550–1900 refers only to "Company" paintings on mica, not to Mughal works of this type.
Still, Swallow offers some hope. He claims that mica was "originally used for festive lamps and the illuminated windows of the taziyas, elaborate model tombs carried by Muslims in the Muharram festival processions. . . ." One of his sources (Skelton) says that according to a contemporary account, "artists were employed to paint sheets of mica for the festival lamps at Murshidabad in the reign of Murshid Quli Khan." Murshid was the nawab of Bengal 1706–1725.
I think it is reasonably likely that mica was known to Indian merchants of our period, especially those familiar with the Bengalese towns of Trichinopoly, Patna, Murshidabad and Benares.
* * *
While India is known for muscovite mica, Ceylon is a source of phlogopite. "In Ceylon, the mineral forms irregular veins, rarely exceeding one or two feet in width, traversing granulite, especially near the contact of this rock with crystalline limestone." (EB1911, "Phlogopite") Unfortunately, the Hammond Atlas doesn't reveal the location of the Ceylonese deposits.
New World Mica
In the United States, we can find mica in several states. Mica resources are identified on the Hammond Atlas economic maps for Alabama, Colorado, Connecticut, Georgia, Maine, New Hampshire, North Carolina, South Carolina, and South Dakota. There was low-level collection and trading of mica by the American Indians in pre-colonial times. For example, North Carolina sheet mica, cut into the shape of a hand, was found at Hopewell site in Ohio. The artifact is from AD 1–400.
However, to acquire significant supplies of mica, we would have to rediscover the OTL sites and mine the mica ourselves.
* * *
The EB1911 article on "Phlogopite" adds that "in Canada it occurs with apatite in pyroxene rocks which are intrusive in Laurentian gneisses and crystalline limestones, the principal mining district being in Ottawa county in Quebec and near Burgess in Lanark county, Ontario." The Hammond Atlas map for Quebec shows mica west of Montreal and north of Ottawa.
* * *
In South America, Brazil and Argentina are both mentioned by the encyclopedias. According to the Hammond Atlas, in Brazil it is found northeast of Rio de Janeiro and Belo Horizonte. It doesn't map out the Argentine sites.
African Mica
Madagascar is famous nowadays as a source of phlogopite mica. Despite Rouse's criticism of phlogopite as susceptible to high power loss, if we can't obtain muscovite mica in quantity, we might need to make do with phlogopite.
According to the Atlas, the Madagascaran mica is near Faradofay (Fort Dauphin), in the southeast. I suspect, from the lack of any reference to it in EB1911, that it was not discovered until later in the twentieth century. If so, then the only way to obtain Madagascar mica is probably to send prospectors and, once they are successful, set up a mining operation.
As of 1632, there was no major European presence in Madagascar; there may be scattered missionaries. Control of the island is divided among several small kingdoms.
* * *
There are three mainland African mica sites: near Louis Trichardt in the Northern Transvaal (South Africa), in Tanzania, south of Lake Rukwa, and in Zambia, south of Chipata. The first of these is probably the one contemplated by the modern EB.
Australian Mica
Close study of the Hammond Atlas would reveal that there is mica in the area north of Alice Springs, Australia. Since that is in the hostile Australian Outback, it is unlikely to be investigated (except perhaps as a sideline to gold prospecting somewhat further north).
Mica in Friendly Territory
So is there mica in friendly territory, that is, in USE-controlled Germany, Sweden, Finland, and the Swedish-controlled Baltic coast? Not to the knowledge of the people in Grantville. Sadly, the atlas offers no clues as to the whereabouts of mica occurrences in Europe, other than in Russia.
But yes, there are modest mica deposits in those areas. Rockhound databases (Mindat) can provide a long list of German, Swedish and Finnish localities where muscovite mica can be found. That, of course, doesn't guarantee that sheet mica can be extracted in a commercially feasible manner.
Just so the storytellers of the 1632 universe know where mica could in fact be found, I have consulted some specialist up-time texts. The results appear below.
* * *
Germany. Chowdhury (183) asserts that Germany produces lithia mica (lepidolite) but no sheet mica. And Rajgartha (104) confirms that there is no "primary production" in West Germany. A 1945 U.S. government report agrees that there is no German mica production. ("Non-Metallic Mineral Resources of Germany," p. 27).
That said, you might find a small "book" of mica here and there. Hochleitner, Minerals: Identifying, Classifying, and Collecting Them has a photo (150) of a nice little muscovite specimen from Bavaria. Its sheets look like they would work fine for a receiver capacitor.
However, even if sheet mica can't be mined in Germany, there is some evidence of early modern use of it there. Rajgartha (3) says that "very small quantities [of mica] were employed by the toymakers of Nuremberg to serve instead of glass, and the waste flakes of mica were sprinkled over carpets and draperies, which were regarded as fashionable when thus decorated. Mica strips were used for mounting microscopic objects and also for sealing zoological objects preserved in spirits." Any early seventeenth-century German use of mica was probably of Russian material, but it is within the realm of possibility that local specimens played a role.
* * *
Finland. The USGS reports that Finland produced 5,591 metric tons of mica in 1994. Rajgartha (93) says that muscovite mica is produced from Kemjawi as a byproduct of feldspar mining, and phlogopite at Siilinjarvi from an apatite mine.
* * *
Sweden. The USGS adds that Sweden is "known to produce mica." Chowdhury says that Sweden produces mica at Gotenborg, and from the Bohuslan district, and that the United States imported 924 pounds from Sweden in 1928. Rouse (357) says that Swedish annual production is in the 50,000 to 250,000 pound range.
Skow (56) claims that Sweden produces virtually no high quality sheet mica. I think that Skow is sadly mistaken. According to Bowie, while the mica in the pegmatite dikes of central Sweden is "generally of a poor quality" (135), the same cannot be said of all of the Swedish deposits. At Essljung in southern Sweden, "high quality transparent muscovite occurs in large flakes and has been extracted." (142) At Brattas, over the period 1885–1994, 132 tons of muscovite was mined (together with 35,000 tons of feldspar and 19,500 tons of quartz). Munkeby also has "abundant muscovite of high quality," and 215 tons of good quality mica was mined there 1942–44.
Perhaps the most spectacular Swedish mica fin
d was in Northern Jamtland, where a "book" of mica was uncovered which was 55 by 85 centimeters (21.7 by 33.5 inches) in surface area, and 18 centimeters (7 inches) thick. (Bowie, 195).
Until USE-trained geologists map the pegmatite fields of Sweden, the USE and Sweden will presumably import muscovite mica from Russia, or possibly, India.
Mica for Our Enemies
As of 1633, the USE was at war with France, Denmark, Spain, the Holy Roman Empire, and England.
* * *
France. Several up-time sources, not available in Grantville, reveal that modern France is a producer of mica. Newman says that France produced 10,000 metric tons of mica annually in 1998–2000, as a byproduct of kaolin mining in Brittany (at Lanvrian and Kerbrient). Even higher numbers are quoted by Euromines for 2000–2002, the figure including "mica recovered from mica schists and/or kaolin beneficiation." Madhukar says that the French kaolin ore is 10% muscovite mica. What isn't clear is what percentage of the muscovite qualifies as sheet mica. It doesn't much matter, since any French knowledge of domestic mica locations would be purely fortuitous.