Grantville Gazette, Volume IX

by Eric Flint

  But that isn't going to stop Richelieu, if he really wants mica. Under the Treaty of Ostend, France was given England's North American colonies, from "Plymouth Rock" to "Jamestown" (1633, Chap. 23). And it sent over a thousand soldiers to the New World, no doubt to make sure that they take control of New Netherlands (New York), too. So, while mica is not one of their principal economic concerns, they certainly can send expeditions to look for it, most likely in Alabama, Connecticut, Georgia, Maine, New Hampshire, North Carolina, or South Carolina.

  Actually, there is mica in Virginia (in the pegmatites of Amelia County); this is referred to in the Audubon Society field guide.

  * * *

  Spain. Bowie says that Spain produced 3,000–5,000 tons of mica annually in 1977–81. There is no reference to this production in the documented sources.

  Hence, the Spanish are most likely to rely on New World sources. Because of the union of Portugal and Spain, the Spanish can develop the Brazilian deposits . . . once they find them. Moreover, the Spanish have certainly seen mica mirrors, and other mica artifacts, in the Americas.

  The Olmecs used mica mirrors as early as 1600 B.C.E. (Hoopes). A Mayan king, buried about 350 C.E., was found with an apron of mica mirrors (Hofstetter). At one site in Aztec Teotihuacan, believed have belonged to a jeweler, over half the soil samples contained imported mica (Storey). The trade routes which brought mica to Mexico should still exist, and the Spanish can exploit them.

  * * *

  Austria. Chowdhury (183) states that there are "extensive mica deposits . . . in Styria and Corinthia in Austria." Madhukar (90) acknowledges the point, but warns that the muscovite is of "very poor quality." It is thus most likely that the Austrians will obtain sheet mica by trade with the Russians.

  * * *

  Denmark. Eventually, the Danes may obtain mica from Norway. Chowdhury (183) says that there is a pegmatite dike, one hundred feet thick, near Skatterlund, which produces sheet mica. Skow (55) agrees that Norway has small quantities of good quality sheet mica. Of course, the Norwegian sources have yet to be discovered by the down-timers, and the up-timers have no inkling that they exist. In the near term, the Danes are likely to go buy what they need from Moscow.

  * * *

  England. The English clearly have imported "Muscovy glass" in the past, and are likely to continue to do so in the new future.

  Prospecting for Mica

  All that the up-timers (or down-timers) know about where to find mica is what is in the encyclopedias or the Hammond Atlas. Nonetheless, they are not without resources.

  First of all, there are definitely specimens of mica in rock and mineral collections. The schools will have them to support earth science instruction, and there are certainly a few rockhounds in Grantville, too. That means that we can show down-time merchants and miners exactly what we are looking for. There are also several field guides documented as existing in Grantville (Mannington), with nice color photographs and additional description of both muscovite and phlogopite.

  Secondly, the Grantville encyclopedias clearly indicate that muscovite micas occur in pegmatites. EB1911, for example, says that "large sheets of muscovite . . . are found only in the very coarsely crystallized pegmatite veins traversing granite, gneiss or mica-schist."

  Popular rockhounding field guides, several of which are available in Grantville, agree. According to the Audubon Society Field Guide to North American Rocks and Minerals, "good muscovite mica specimens are restricted to granitic pegmatites." Pegmatites are light-colored, coarse-grained igneous rocks, and they, too, are going to be found in those rock collections and field guides.

  Now, pegmatites are famous as hunting grounds for large crystals. If those crystals have certain other properties, like hardness, then we have another name for them: gems. So we may be able to find a likely mica locality on the basis of mica's association with something the down-timers are more interested in, that is, a gemstone. EB1911 says that the pegmatite "veins consist of felspar, quartz and mica, often with smaller amounts of other crystallized minerals, such as tourmaline, beryl and garnet." The Audubon Society guide mentions associations with quartz and tourmaline. The entry on "granitic pegmatites" has a long list of minerals, which includes beryl, opal, topaz and zircon.

  Brown's specialist book on Indian minerals says that "the beryls of the mica-bearing pegmatites of India, in which they often attain huge dimensions, are too fissured and flawed and of too washed-out a colour to be of any value in the gem trade." (598) Still, I would expect that jewel merchants would know something of these giant beryls, assuming that they had in fact been mined at this time.

  Beryl is of interest in its own right as a source of beryllium, and Brown indicates that the productive beryl deposits in India are the pegmatites of Rajsthan, Bihar and Andhra, and that it is "recoverable in small amounts as a by-product of mica mining, particularly from the Koderma Forest area of Hazaribagh and the mica mines around Gudur in Nellore." (268–9)

  Chrysoberyl is also of interest; Brown says that "transparent yellow stones of good quality occur with beryl in mica-bearing pegmatites at Govindsagar, Kisangarh, Rajasthan." (603).

  Another association is with aquamarine (a gem variety of beryl); "some beautiful aquamarines have come from the mica mines, 1 1/2 miles west of Saidapuram, Nellore." (Brown, 598)

  Phlogopite micas are found in marbles, and hence it may be productive to question sculptors, and check out the marble localities in the Hammond Atlas. In OTL, the main commercial sources of phlogopite were Madagascar and Canada. (Brown)

  Mica Mining and Processing

  Mica is split into sheets, trimmed, and sorted, almost entirely manually. Splitting is done with a knife. Twentieth century attempts to make machines which could split mica "books" into sheets of specified thickness were unsuccessful. Trimming and sorting are even less suitable for automation, as they require judgment. It is a good thing that the up-timers are now in a world in which labor is inexpensive! Trimming can be done by finger pressure, or with a knife. (Rouse 244–5).

  Mica Mine Productivity

  The larger the sheet, and the higher the quality, the rarer it is. At one Indian mine, the workers extracted 123,200 pounds of rock daily, of which 7,500 pounds (6%) was "rough mica." Preliminary sorting reduced this to 5,000 pounds. Splitting and trimming yielded just 1,000 pounds of unsorted sheet. During sorting, some additional trimming had to be done to take out flaws, leaving 932 pounds. (Rouse, 354)

  The grade distribution of these sheets was 38.5 pounds clear, 90.95 pounds slightly stained, 26.85 pounds fair stained, and 775 pounds stained. The size distribution was 0.2 pounds of Special (36–48 square inches), 1.3 of No. 1(24–36), 3.9 of No. 2(15–24), 15 of No. 3 (10–15), 30.4 of No. 4 (6–10), 100 of No. 5 (3–6), 61.6 of No. 5 1/2 (2.5–3), and 720 of No. 6 (1–2.5).

  Suppose that for a transmitter capacitor, you want sheets 24 square inches or larger, and of quality better than stained. The daily output of such material from that Indian mine was just 0.9 pounds: less than one part in one hundred thousand of the total rock excavated.

  USE Mica Demand

  In general, for a transmitter capacitor, you will need higher capacitances than for a receiver capacitor. To achieve a high capacitance, you want the dielectric to be as thin a sheet as its dielectric strength permits, and you want to maximize the effective cross section (the surface area of one flat dielectric sheet, times the number of those sheets). A typical thickness for a mica sheet is two mils (i.e., two-thousandth of an inch).

  For a mica transmitter capacitor, we want a stack, one to three inches thick, in which a conductive (c) material (gold or silver foil) is interleaved with mica (m) sheets, like so: cmcmc . . . mcmc.

  A transmitter capacitor will use perhaps forty square feet of mica, and have a capacitance of around four microfarads (4,000,000 picofarads). This could take the form of a one inch stack of alternating metal and mica sheets, in which there are 250 two mil thick mica sheets, each four by six inches. (Boatright,
personal communication). The total mica content is 11.52 cubic inches. The density of mica is about 300 kilograms per cubic meter (0.0108382 pound/cubic inch), so one transmitter capacitor needs one-eighth of a pound of high quality sheet mica.

  If there was demand in Europe for 1,000 transmitter capacitors, you would need 125 pounds of suitable sheet mica. That doesn't sound like much, until you realize that you would probably have to process 12,500,000 pounds of ore in order to recover the sheets you wanted.

  * * *

  A receiver capacitor for a crystal radio only needs 10-20 picofarads of capacitance (Boatright). For that, we don't need mica, just an air gap will do. However, a mica capacitor would increase the sensitivity of a crystal radio.

  For the sake of argument, let us say that the receiver capacitor uses a single two mil thick sheet of mica, just a quarter inch on each side. That would have a capacitance of about 40 picofarads.

  There are perhaps eleven million people in the USE and Sweden. Let us say 10% eventually obtain crystal radios, and that 10% of those sets are equipped with mica capacitors. If each set has two capacitors, then we need 22,000 of them. The individual receiver capacitors only use 1/100,000th as much mica as the transmitter capacitors. It is clear that the scrap from mining for transmitter grade capacitors will supply our needs for receiver capacitors.

  Mica Economics

  If the only mica which has economic value is that which was in large sheets of transmitter capacitor quality, then mica would be extremely expensive to mine. If you take only one pound out of every hundred thousand pounds of rock mined, and just toss away the rest, then you are talking about a very labor-intensive operation. Labor is cheap in the early seventeenth-century world, but not cheap enough.

  Pliny, in his Natural History, refers to what is translated as "specular stone" or "mirror stone." Translator John Bostock assumes that this is "transparent selenite or gypsum." However, since Pliny says that it "can be split into leaves as thin as may be desired," it seems more likely that it was mica. EB1911 agrees.

  The principal use of the Roman "specular stone" was in buildings. This may well have been in windows, in which case it antedated, by many centuries, the Russian use of "Muscovy glass."

  Mica, besides transmitting light, is also heat resistant. For this reason, it has been used in more specialized windows; for example, as a stove window ("isinglass"), or in the panels of a lantern.

  In pre-electric nineteenth-century America, mica was used mainly for oven windows and gas lamps, and that meant that the demand was limited to sheet mica. The requirements weren't as stringent as for capacitors, but some deposits couldn't be mined because they didn't produce sheet mica in quantity, and what mines were worked produced plenty of waste.

  That changed in 1878, when Edison invented the electric motor. Not only did the motor require electrical insulation, that insulation had to tolerate heat. Mica was ideal, and scrap mica did the job. This could be assembled into built-up mica, or ground mica could be used to make micanite. What had once been waste mica had become a commercial product, and that changed the economics of the industry for the better. (Anglin)

  The sparkle of mica (which is called "glimmer" in German) also gives it a decorative function. Pliny says that, at the "celebration" of the game, the sands of the Circus Maximus were strewn with the "shavings" and "scales" of the mirror stone, "with the object of producing an agreeable whiteness." The modern equivalent is the incorporation of mica powder into the sidewalks of Hollywood, so they sparkle.

  Mica powder also can be mixed into paints and cosmetics. In Federico and Ginger (Grantville Gazette Volume Six), Adriane's skin has been "liberally sprinkled with twentieth century 'moon glitter' to give her a more celestial appearance." Her "glitter" was nothing more than wet ground mica.

  While this variety of uses makes mica mining more practical, large sheets are likely to be disproportionately more expensive than small ones. In 1911, an "average" sheet price was four shillings a pound, while large sheets could cost as much as fifty-four shillings a pound (EB1911, "Mica").

  Mining for Associated Minerals

  The economics can be improved further if some of the associated rock isn't really waste, but rather can be used for something else.

  It is not unusual for mica to be extracted as a byproduct of feldspar mining, or vice versa. Feldspars are aluminum silicates, and the "alkali feldspars" also contain sodium or potassium.

  Feldspars are not a "strategic material" like mica, but they have their uses. Alkali feldspars are used as fluxes in the manufacture of glasses and ceramics. The alkalis (sodium and potassium) act to reduce the melting point of the composition. The aluminum makes the glass harder, stronger, and more resistant to chemicals.

  Feldspars are also used as fillers in rubbers and plastics. Since the USE supply of rubber and plastic is limited, that may come in handy.

  * * *

  Micas may be associated with beryls. Beryls are beryllium compounds, with a beryllium content of about 4%. Gem varieties include emerald and aquamarine. Material which falls shy of faceting quality is mined nowadays as a source of beryllium.

  Like aluminum, beryllium is a light metal. Beryllium can be alloyed with copper or nickel.

  Synthetic Mica

  The Encyclopedia Americana mentions that synthetic mica had been developed, but provides no clues as to how it was produced. Hopefully, one of the chemists in the USE will know that the synthetic mica was not considered a success, so the USE will not squander resources on an attempt to duplicate it.

  Conclusion

  There are two reasons why it is worth taking a look at how mica might be exploited in the 1632 universe.

  First, there is a window of opportunity in which mica will play an important role in radio development. This will be the period in which Europeans rely on spark gap and arc transmitters. Bear in mind that even after the USE shifts to more advanced, vacuum tube- or transistor-based equipment, some of our rivals will still be using the older technology.

  Secondly, this study provides a sampling of the problems which the up-timers face whenever they try to get their hands on a familiar raw material. You can't just order sheet mica (or rubber, or borosilicate glass, or gasoline, for that matter) over the phone or internet, and have it on your doorstep a few days later.

  * * *

  While some might prefer the glitter of gold to that of mica, the latter is precious in its own way.

  Bibliography

  Mica, Generally

  Rouse, Chapter XII, "Mica," in Strategic Mineral Supplies

  Chowdhury, Handbook of Mica (1941)

  Spence, Mica, its Occurrence, Exploitation and Uses (1912)

  Skow, Mica: A Materials Survey (USDI 1962)

  Rajgarhia, Mining, Processing and Uses of Indian Mica, with Special Reference to the Bihar Mica Fields (1951)

  "Mica Introduction,"

  http://www.icrmica.com/icrmica_mica_introduction.html

  Cole, "Mica,"

  http://www.science.uwaterloo.ca/earth/waton/f0102.html

  Anglin, Women, Power and Dissent in the Hills of North Carolina ; Chapter 3, Mica Mining, is available online at

  http://www.press.uillinois.edu/epub/books/anglin/ch3.html

  Mineral Information Institute, "Mica,"

  http://www.mii.org/Minerals/photomica.html

  USGS, "Mica Statistics and Information," http://minerals.usgs.gov/minerals/pubs/commodity/mica/

  (Mineral Commodities Summaries for Sheet Mica 1996-2005, Mineral Yearbook for Mica 1994-2004, Historical Statistics for Sheet Mica) and

  http://minerals.usgs.gov/minerals/pubs/commodity/mica/440494.pdf

  Glover, "The Spruce Pine Mining District [NC],"

  http://www.mitchell-county.com/festival/spminingdistrict.html

  Answers.Com, "Mica,"

  http://www.answers.com/topic/mica

  Works on Mineral Resources

  Mindat, "Muscovite" entry at http://www.mindat.org/

  (detaile
d locality info available)

  Bowie, Mineral Deposits of Europe, Vol. 1, Northwestern Europe (1978)

  Newman, The Mineral Industry of France (USGS 2000), http://minerals.usgs.gov/minerals/pubs/country/2000/9414000.pdf

  Euromines, "France: Production of Mineral Commodities,"