EIGHT PETROGRAPHIC STUDENT AND LAB MICROSCOPES FROM THE GOLDEN YEARS
by J. Gregory McHone, Canada
College and university students of geology in the USA during the 1960s and 70s (I was one) were often introduced to the petrographic microscope after a course of mineralogy, perhaps coincident with their first semester of petrology, or the study of rocks. We learned a big part of geology by the examination of minerals in rocks, which quite literally comprise the Earth. You can not know geology without knowing rocks and minerals, and you can only study minerals in rocks by using a petrographic microscope. At least one semester of optical mineralogy and petrography was a common requirement for everyone in the major, although this is only rarely the case today (don't get me started on how our science has been watered down by other topical subjects).
A teaching lab for optical mineralogy might be equipped with a dozen or so student or "lab" models of petrographic polarizing microscopes. Then as now, they were a big budget item for the department, perhaps spread over several years of purchasing a few scopes at a time. After decades of use and disuse, several makes and models of student microscopes of various ages and conditions could be found in a typical geology department. For example, the lab where I spent many long evenings puzzling my way through junior and senior optical assignments had pale mustard Vickers M14s, black Zeiss Juniors, a black horse shoe foot B&L or two, and I think a black Leitz with a U-stage mounted on it (a universal stage can be rotated in all three dimensions to study single grains). Zeiss and Leitz from West Germany were held in highest regard back then, but at different schools you might also find some student models by Vickers, Zeiss Jena (East Germany), Reichert of Austria, Bausch and Lomb, American Optical, and Olympus or Nikon. The Japanese brands were rather looked down on without much reason, and later I found them to be very capable and well made instruments, not at all inferior.
Micscape has presented several useful articles on petrographic scopes and polarizing equipment. In the June 2003 issue, Ian Walker described a custom pol filter setup on a gray biological Zeiss Standard, followed by an interesting review of the JNOEC XPT-7, a Chinese horseshoe-foot microscope which probably is the least expensive new petrographic microscope on the market. I once had one in my shop that I eventually sold to a retired geologist in Arizona. It was a perfectly functional student-grade microscope with good optics, but something of a design anachronism, and not up to the high standards of fit and finish that you will find in an older major-brand instrument.
In the October 2006 issue of Micscape, I described six of my favorite benchtop polarizing petrographic microscopes that (with luck) you might find on internet auctions or even dealer websites for about $1000, more or less. Even after 25 years or more of use, these instruments remain very capable and desired by those of us who are still serious about geological microscopy, but their prices might still be too high for more casual interests. A wider audience exists for student or lab microscopes from the latter decades of the 20th century. Many amateur or professional scientists will find one to be perfect for home use, and It can also be a great gift to a young person, perhaps a budding science hobbyist or a new college geology student. I have seen many examples for sale at prices between $300 and $800 (at this writing my Canadian dollar is almost par with the once-mighty USD, and about $2 is close to 1 GBP). This is a small fraction of their new cost, and one in good condition can be a great bargain.
As you probably know, the interesting variety of classic microscope brands were mainly whittled down to the "big four" of Zeiss, Leitz, Olympus, and Nikon by the 1980s, and Leitz became part of Leica. With the decline of optical mineralogy as a course requirement after the 1990s, many of the fine old student pol scopes from earlier years became surplus and have entered the private market of used microscopes. As might be expected after years of student use and sometimes abuse, perhaps followed by long neglect stored away in a back room, these older pol scopes show a great range of quality, condition, and completeness. This article concerns examples of such microscopes that you might obtain from a dealer or an internet source such as eBay.
Problems and Possibilities
Some expert advisers will warn you away from microscopes that were or might have been part of a college student microscope lab. Having taught optical mineralogy myself, I know about the abuses, both innocent and willful, that are common for these older workhorses. Many, perhaps most, have been dropped some distance onto a hard benchtop or floor at some time. Food and drinks are regularly spilled onto and into lab microscopes, followed perhaps by a crude cleaning with rough paper towels. Oils from refraction index measurements, particles from rocks, dirt from hands, and dust from the air are collected onto and ground into stages, knobs, lenses, gears, and frames. If an objective can be lowered to break a glass slide or rotated to hit a mechanical slide holder, it has been. Many attempts have been made to overcome resistance to limits of travel for focusing and movement of various accessories -- and some of these attempts succeeded. I have also seen some fine old scopes reduced to basket cases by their use in thin section labs as "mules" for checking the thickness of rock sections as they are ground on a lap. A hard gray cement could be found in every place that a liquid slurry of carbide rock grit might penetrate.
Lenses and optical filters in student microscopes are sometimes damaged by heat from their incandescent lamps. Possibly the best brand, Carl Zeiss of West Germany, has the worst reputation for this problem, due to their particular optical cements that could delaminate and fog optical layers in objectives and polarizing filters. It is common for students to use lighting at high power settings (closing down the field lens for more comfort), and to leave it cranked up for many hours at a time, even while taking a cafeteria break. Infrared radiation from the white-hot lamp filament permeates the optical elements to cause the damage, most commonly to a polarizing filter, which is less expensive but not easier to replace than an objective.
But as any repair technician can tell you, the best brands are also the most serviceable. The care and quality that went into major-brand microscopes, including their student models, means that moving parts have resisted wear, dirt can be cleaned from their durable surfaces, accessories and light paths be re-adjusted, gears re-lubricated, and most of it can be disassembled and reassembled back to original specifications. The abundance of older student microscopes means that many parts and accessories are available in today's used market (especially on eBay but also by professional dealers). Not just good optics and functionality but also service and durability define quality: major reasons why universities and research companies favor the big four brands, even though they could buy twice as many generic microscopes for the same budget. These are the same reasons why people like me continue to recommend well known used microscopes over unbranded new ones.
Their stands might be smaller and somewhat simplified relative to the full-sized benchtop models from the same maker, but that is not a reason to shy away from a student microscope. The top companies lavish the same expensive care with quality and construction on their student models, including the same optics as offered for the research lines, and often other accessories are the same as well. Most older polarizing microscopes at all levels use achromat or plan achromat objectives and condensers, because their fewer optical layers create fewer problems of induced birefringence, or slight polarizing effects where they are not wanted.
Eight Student and Lab Scopes
I am not a professional microscopist or trained service technician, but rather a teacher and microscope user for almost 40 years. I also fix up old microscopes as a hobby; for myself, not for others. Some I use in my lab, some sit on a shelf to admire or for future activities, and others are (eventually) sold on eBay. Models I have personally used as a student include the black Zeiss Junior and the Vickers M70. My examples neglect Nikon, which was not particularly common in geology labs during the 60s and 70s. It is my loss to not encounter many Leitz pol scopes during my college years, outside of the Dialux in the Micscape article cited above, and a fantastic Orthoplan Pol that my chairman let me use a few times. That Orthoplan, in my considerable experience, was the finest petrographic microscope I have ever used.
The following illustrations and comments describe eight of the more interesting smaller petrographic polarizing microscopes that you might consider for personal use. I like them all, but they are presented by alphabet order, not by my ideas of desirability. These and others are illustrated on my geological microscopes website.
Leitz SM Pol
Thanks to Dirk van der Marel (eapoecistron on eBay), here is a photo of a well-maintained Leitz SM ("Student Microscope") Pol, which was a popular lab and teaching scope from the 1960s. I have a monocular Labolux pol scope in my shop with a similar stand and bayonet-mount head, except the base in the Labolux is thicker so it can hold an internal light source. The fine optics and quality found in larger siblings are also in this SM model, but of course this simpler external light source is not quite as good for photography, although fine for eyesight. For lighting, you could choose among this 15-watt 110-volt lamp (or 220-volt in Europe), a 6-volt 5-watt lamp with transformer, or a mirror.
Rather than in an intermediate tube, the analyzer is built into the arm just below the head and is flipped into the view via a side lever (visible above), while the Bertrand lens is in the viewing tube. The polarizing filter beneath the condenser can be rotated, and there is an adjacent slot for a 4x12 mm wave plate. There is another slot for a wave plate in the inside back of the nose turret, and the view is centered via spring bolts on either side of each objective, not by the stage. The turret is permanently attached and can hold four objectives, but three "P" achromat objectives were part of the basic package: a 3.5x/0.10, 10x/0.25, and 50x/0.85, to be used with the standard 8x pol Huygens eyepiece. Two stage clips were standard, but the mechanical X-Y slide holder in this example is a very nice accessory made for all Leitz circular stages, and it was also available in a version with click stops for point counting. The single axis knob works well for both fine and coarse focusing.
The black Leitz SM-Pol and Labolux-Pol apparently both have fixed nose turrets, as well as a bayonet head mount for their monocular heads. Higher-level models have a removable turret than slides into a dovetail, and for their binocular heads, a little tab on the arm engages a circular head flange. Leitz had so many microscope variations, accessories, models, and versions that inventory control must have been a nightmare, and not good for efficient manufacturing and marketing. But it adds lots of interest for us fans of their microscopes.
By 1970, there were six models of polarizing microscopes marketed by Leitz. From small to large, these were the SM-Pol, Labolux-Pol, Dialux-Pol, Epilux-Pol, Ortholux-Pol, and Orthoplan-Pol. According to my 1971 catalog, the SM-Pol cost around $1300 in its basic configuration. Leitz was a major player in the polarizing microscope market, as shown by that large catalog full of parts and accessories for these models. All were made at an absolute peak of excellence.
LOMO Min 1
I don't know if this microscope was widely used for student instruction at universities in the Soviet Union, but it certainly fits my "smaller" lab scope criterion. I bought this field microscope on eBay from a seller in Russia. It looked too interesting to pass up, and the final bid price was very low. It arrived loose in a large burlap sack with a label and stamps stuck on the coarse cloth, no padding or packaging whatsoever. Never seen anything quite like that before. If not for the sturdy field case it came in, the microscope would surely have been damaged beyond repair during shipment. The hard aircraft aluminum case is the size of a lunch box, about 27 by 23 by 11 mm (11 x 9 x 5 inches). Once assembled it stands about 28 mm (11 ") tall. The diminutive field scope inside was complete with three oculars, three objectives, and two 4x12 mm compensating wave plates. My translation of the Russian label on the stand is Min-1, one of several Min or mineral analysis models made by LOMO in past years. Dirk Marel once had a black enamel benchtop pol scope on eBay called a Min-8, and I have also seen a reference to a Min-6. A search of the internet and an email to LOMO provided nothing about LOMO Min series scopes.
When assembled, the microscope is not much larger than a toy scope a child might own, but this is no toy! The clip-on objectives are full size short-barrel types that were common in the 1970s, and the head and eyepieces are also of normal dimensions. The analyzer is on a sliding plate above the nose clip, while a swivel Bertrand lens is in the head. The small circular stage works OK but is not centerable, as the objectives are centered in their clips with a couple of small hex key wrenches, included.
In design you can detect its early Zeiss Jena (East Germany) kinship, with the entire arm and head moved for focusing. Fit and finish are quite plain and utilitarian, but the construction is robust and operation is smooth and functional. The optics were adequate, probably not much different from its larger cousins, but not up to more modern standards. Of the eyepieces, the low powers were OK but the higher power almost worthless. You could probably swap out optical parts easily enough, as they are standard sizes, although the small condenser might be special to this stand. This model is so rare and so interesting, I wish I had kept it.
Field microscopes can be very useful in biological work, and probably this petrographic scope could also be used for mineral samples such as soil and crushed grains. In the olden days, we would scrape off rock particles into a drop of immersion oil on a slide, and attempt identification via birefringence and relief characteristics. A rock section is much better, but it would be a real trick to make a 30 micron thin section of a rock while living in a field tent, far off the grid!
Meiji claims to be right behind Nikon and Olympus among Japanese microscope companies, and until recently at least, it was the last company to still make all of its scopes in Japan. They are widely advertised in geological trade magazines. In design the ML series has some similarities with the Olympus CH-2, and thus are aimed at both student use and routine laboratory operations such as asbestos identification (as opposed to higher-level research). It is definitely a 1980s style that has continued in production, with 30-watt in-base halogen lighting, 45-mm focal length objectives, and a 160 mm tube length light path that incorporates an intermediate tube for the analyzer, Bertrand lens, and compensating plates (6x20 mm size). These all function via sliding plates inserted into tube slots. This one was also equipped with a very nice X-Y slide holder, made in the pol-scope style with flat control knobs so they do not interfere with the objectives as the turret is rotated. There is a focus movement limit that can be set to prevent the stage from hitting an objective. It also has a diaphragm before the field lens and an adjustable condenser, to assist with Kohler-type even illumination. All very professional.
Just in the past year or so have I noticed that Meiji has brought out a newer infinity tube length MT series, although I expect dealers still have these venerable ML models in stock. Certainly the ML looks "modern" relative to the other microscopes in this review.
The few Meiji pol and biological microscopes I have used have been honest, smooth operating machines with good optics and good design. This one is full sized but still light enough to be fairly portable. Not particularly robust, nor does it have the superior mechanical feel and polished construction of the big four, but the ML9200 is nice to use, very functional, and relatively easy on the budget both new and used.
When styles shifted away from black enamel and horse shoe feet after the 1960s, major retooling was necessary by microscope companies. Some older models were continued anyway, but freshened up with new colors (also see the Vickers, below). Olympus marketed this smaller student model into the 1970s, even after they introduced the BH line of larger benchtop stands, which was certainly a major design effort. However, there was also no stinting on quality in this smaller student model. It has excellent fit and finish with a nice "hand feel," and tight, smooth, no-rattle connections. It came with a mirror for lighting, but I added this plastic 15 watt light source because it fit so well and lamps are more convenient for indoor use. Like most models in this older style, the analyzer and Bertrand lens are mounted in sliding plates in the main tube, not in modules that were becoming normal for larger instruments. Of course, the tube and stage were installed in the same stand that was used for the more abundant biological versions.
I am not enthusiastic about clip-on centerable objective holders, which I suppose are easier to manufacture than a centerable nose turret and also obviate the need for a centerable stage. The clips work well and are quick to change, but you have to stop what you are doing and find the next one in a box, making it awkward to shift powers frequently, as I tend to do. Overall, in my opinion this is the best of the old-style student microscopes, nicer than horse-shoe-foot scopes I have used by CTS, Vickers, American Optical, Bausch & Lomb, and others.
From my years as a student and full-time faculty member, I cannot recall using any Reichert of Austria microscopes. Later as a program administrator and part-time adjunct instructor at several local colleges, one program where I taught had a few scopes like this one, which I eventually learned is a Neopan. You may be more familiar with the much larger Zetopan, which despite homely looks had a good reputation for quality and function. This smaller model felt a lot like a Zeiss Jena, meaning not particularly solid, but it certainly worked well.
The focusing mechanism mystified me at first, but eventually I saw how to use it properly. The large knob turns for the coarse focus as you would expect, but then to fine-tune it you don't turn the knob but instead swing it horizontally front to back. You can see the slot to allow this movement in the side of the stand. It actually works quite well. A monocular head is present on the few other Neopan pols I have seen, and I think that the binocular head on my example is from a biological version, as it did add a slight birefringence to the view (i.e. it was not strain free). Also there is no way to keep a cross hair ocular aligned with the view axis when you adjust the eye tube separation on this Seidentopf style head. Zeiss had a version with a special gear for that purpose, which I have not seen in other brands.
More recently I obtained this Reichert trinocular head and incident (reflecting) light tube, which I think is for the Neopan. Alas I now have no stand for it, as yet. There is a sliding polarizer for the incident tube and an analyzer slider, and I think a Bertrand lens as well. The upper knob switches the light path for the photo tube. However, as on my example above, the eyepiece tubes are not really designed for a cross hair ocular, which of course every petrographer needs (see my article in the August 2008 Micscape).
The M14 and M70 are very similar models from Vickers, which they converted from black enamel stands formerly produced by CTS (these British companies merged in the 1960s). At one time they were common at American geology programs, at least at the several I have known. I assume they were much less expensive than the Zeiss scopes that we students preferred over all else. Later in my first job in mineral exploration, I bought one of these for my personal use from a private college that sadly went bankrupt. It went cheaper after the auctioneer said it was missing an objective, but it was not -- the 3x is so flat that it looks like a hole cover. The microscope served me very well for many years, and I still look back at it with fondness (it was sold to help finance a much more expensive Olympus BH-2).
This M70 has centerable objectives, not something you see too often on student Vickers (most have a large stage that can be centered, but there also is a smaller size that can not). The objectives on this example are 5x, 10x, 20x, and 40x. Vickers strain-free pol objectives use red lettering, but the regular biological versions (black lettering) are mostly OK on it as well. A few examples I have encountered had a loose stage carrier connection, but they were easily fixed by tightening the rails under the front covers behind the carrier. Many mechanical and light-path adjustments are possible in this stand, and some might be needed after a few years of usage, but they are not hard if you like to tinker.
The company used a modular intermediate tube for the analyzer, but the special monocular pol head held the built-in Bertrand lens (some have a lower dual knob that swings it in, while the smaller knob can focus it). There were also two eyepiece tube sizes for different head versions, the larger one close to 29 mm in diameter and thus providing a bigger view. The bolt-on lamp holder between the feet looks somewhat primitive, but the lamp tube can be adjusted to properly center the filament. As in the Leitz, there is a slot for a 4x12 mm wave plate in the back of the nose turret.
Optics were good and the pol operations function well. Although I clearly recall as a student that a good conoscopic figure was hard to obtain, later with my own instrument I had no such problem. A clean example, not worn out by too many years in college, is still a fine tool for any student or professional for home or field use. And built like the proverbial tank.
During the cold war years, Zeiss of East Germany could be marketed in the USA only by distinguishing its name with Jena, the home city location, as separate from Carl Zeiss of West Germany. In the mid-1980s we were somewhat surprised that a "communist" brand was allowed at all. But the price was low and quality seemed decent, so they were happily grabbed up by several programs. This was a student model, which I found to be somewhat similar to Reichert in looks and feel. There was also a larger benchtop model called the Amplival, which had a similar faceted angle base and semi-glossy greenish gray finish. No doubt the same optics are in all the models. This one might be an early version of the Laboval, but I am not up on all of the Zeiss aus Jena designations.
A couple of them passed through my shop with electrical problems and frozen focusing gears, which I did not try very hard to fix (it was not a repair commission, only movement through me from a museum back to the college owner). I have read mixed reviews about the reliability of this generation of Zeiss Jena scopes. But their optics appeared to be adequate, and the fit and finish reasonably good. Certainly it is interesting, which to me is always a plus. If they can be serviced to good operational condition (that's a big "if"), one of these might be nice to have in your home lab. Sorry I did not keep one to work on, as I like the challenge.
As I mentioned above, students and instructors in my programs generally preferred Zeiss pol scopes when given a choice among several models. It's not that they were a lot easier to use, especially with the pesky 2-ring centering on the objectives. The objectives were not particularly parfocal either, the older Kpl 8x oculars did not provide a very wide view, and the lighting was none too bright at higher powers. But when you are using one, the quality just flows from the machine into your hands and it becomes a real pleasure. I have had several Zeiss pol scopes and I like them a lot, as do most people who have used them.
This is the Junior model, which has a small round base and an external "flashlight" type lamp holder with a 110 volt 15 watt bulb. You should use a GFCI outlet with such direct-voltage instruments. In the 1970s, many programs started to buy new gray monocular Zeiss Standards, either with a lamp tube in the base connected to an external transformer, or with a 10-watt halogen lamp and transformer built into the base. I have already described one of those gray Standards in my October 2006 article, so I decided to show you this older black enamel model. These 160 mm tube length optics remained the same as those used in later Zeiss pol scopes right through the 1980s, including high-end research models, except later eyepieces provided better wide-field viewing. You must hold both rings on each objective so they can be turned independently, which move small cams to change the center of view. The trouble is, when they are new they can move too easily and any little bump when you rotate the turret shifts the view center. Some years later, they get stiff and are a bear to move independently. A nose turret with centering bolts is better.
Many Zeiss pol scopes of this vintage show some breakdown or delamination of the analyzer pol filter. I once inspected eight black Zeiss scopes in a college lab in which every one had this problem. A little fogging around the edges will not make much difference, while if it is bad enough, the head can be disassembled and the filter replaced (you might need to search a while to find one of good quality in the right size). Sometimes the polarizing filter is damaged as well, but only rarely have I seen problems of optical fogging in these pol objectives. The objectives can also be disassembled to lubricate sticky centering rings, but it is a job that might best be assigned to a professional technician.
As students, we were certain that the Zeiss Bertrand lens (built into the monocular tube in this example) along with the other optics provided a superior conoscopic figure, leading to better results in lab exercises (thus better grades). Well, maybe an instrument like this just builds confidence.
Something about microscopes, especially petrographic types, makes them endlessly interesting. I like the variety of designs and mechanical systems among these older models, and if I had the space and finances they would all stay in my shop to admire, and perhaps to use on occasion. But when they are all fixed up, it is time to move them on so I can afford parts for several other project scopes that are begging for attention (I can hear them calling to me even now). That's a hobby. You, however, might want one to actually study rocks and minerals, and if it doesn't meet your expectations, you will trade up for one that does. There are more every day in the used market to chose among, and perhaps one of the microscopes illustrated in this article will come your way.
Published in the September 2008 edition of Micscape.
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