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Microminerals.

Sunday, July 12, 1970, was a hot, clear day in the quarries on Mont Saint-Hilaire. There had been a blast in what was then the De-Mix quarry (the center one of the three) on the preceding Friday, and there was a large fan of rubble stretching out on the quarry floor from the back wall. I was sitting half-way up the slope working on a mediocre boulder when I spied a small mobile dot entering the quarry. The dot turned into Dr. Peter Tarassoff, who had been away for several weeks and was on his first visit to the quarry in some time.

Peter climbed up the rubble slope toward me, said "Hi" on the way by, and proceeded to the newly exposed back wall, where he stuck his hand under a rock slab and began hauling out large analcime crystals (up to 10cm!). He had hit such a bonanza that he had to go find a couple of dynamite boxes left by the workers to pack them out. Aside from drooling a little, there wasn't much I could do at the time, but I did scavenge a bunch of the gravel from the bottom of the vug later on.

On examination, even the gravel proved to be very productive. There were aegirine crystals with oddly clubbed ends; pale pink, blocky ancylite crystals; spiky balls of calcite; very complicated, water-clear crystals of an unknown mineral; tiny, resinous brown crystals of a second mineral showing a hexagonal pyramid termination, and pale brown sprays that were obviously astrophyllite.

At home, a UV lamp gave a nice green glow to the water-clear crystals. Under the microscope, their complicated habit became roughly tetrahedral. That added up to genthelvite. The hexagonal brown crystals turned out to be hemihedral. That suggested wurtzite. The astrophyllite was so characteristic in shape, so much like small twig broom heads, that I called it witches' broom astrophyllite.

A couple of years later, I handed a sample to the staff at the Smithsonian Institution. Dr. Pete Dunn checked the genthelvite, and described it as end-member material, with no iron content. Dr. Arthur Roe mounted a single crystal of the brown material on the Gandolfi camera, and confirmed that it was indeed wurtzite. Other studies later showed the ancylite to be calcioancylite-(Ce). [1] The witches' broom astrophyllite was merely pretty, but nice, so I sent samples to a number of collectors as an item of interest from Mont Saint-Hilaire.

Over the next 30 years, I sent a lot of witches' broom astrophyllite to people in various parts of the world.

Ottawa, Canada's capital city, has two universities and a lot of research capability. One of the researchers, Paula Piilonen, a Ph.D. candidate at the University of Ottawa, was also a member of our micromounting group. A couple of years ago, she mentioned that she intended to do her thesis work on astrophyllite. I showed her my witches' brooms, and gave her some samples, as did Dr. Tarassoff, the original finder of the vug. Shortly thereafter we heard from Paula. The witches' broom astrophyllite proved to be a new species-niobokupletskite. To be specific, it's Type III niobokupletskite (see Mandarino, Mineralogical Record, vol. 32, no. 3, p. 218).

So--what's the point of this story? There are three points:

(1) In the amateur community, it's usually the micromounters who find the new minerals.

(2) New minerals don't have to come from yesterday's field trip. They could have been in your basement for 30 years.

(3) Everyone who has a specimen labeled "Witches' broom astrophyllite" should change the label to read "Niobokupletskite (Type III)."

Actually, exactly the same thing happened with ferroceladonite. It appeared in the late 1960's as the green mud that collectors spent hours washing away from their epididymite and elpidite specimens at Mont Saint-Hilaire. We had it in bucketfuls and paid no attention to it, except as a nuisance. It was described as a new mineral in 1998, using infinitesimal scraps of material from a locality in New Zealand. The lesson is simple: go over your collection again and again, and really pay attention to the accessory minerals.

SOME STATISTICS [2]

Mont Saint-Hilaire is the current Mecca for collectors of microminerals. Glossy magazines print colorful shots of its gorgeous crystals, and collectors salivate at the prospect of the next finds. What people tend to forget, is that the Poudrette quarry (it's all one now) on the Magic Mountain is there for commercial aggregates. The quarry was opened in 1954 to provide roadbuilding material for Autoroute 20 between Montreal and Quebec City. Today, it produces 150,000 metric tons of shingle stone and 500,000 tons of construction aggregates per year, using special techniques to crush and screen on-site.

Shingle stone is the term used for the fine granules stuck to the asphalt shingles on the roof of your house. It is made of crushed hornfels (referred to in the commercial world as "trap rock"). The hornfels is good for this purpose because it is low in iron. That means that it doesn't produce rust streaks down the sides of the house as it weathers. It takes 2.75 tons of horofels to produce 1.50 tons of shingle stone.

Construction aggregate is made from the syenite bodies. It is crushed to 14-20 mm for asphalt or ready-mix; 5-14 mm for concrete aggregates; 5-10 mm for asphalt stone, and so on. Hornfels is processed from 6 am to 3 pm and syenite from 3 pm to midnight to prevent cross-contamination.

SOME STATIC

Nobody likes minerals with acicular habits. In the first place, they break too easily. In the second, when they do break it's usually because most of the tip has just buried itself in your finger, and you are going to have to spend the rest of the evening digging it out. In the third, those miniature hedgehogs collect hairs. Take a look at any cluster of acicular crystals under the microscope, and there are usually half a dozen little dust hairs of one kind or another wound between the needles.

Over the years, there has been plenty of depilatory advice given in books on mineral collecting. It has ranged from blasting with compressed air to passing the specimen through an open flame in the hope that the hairs would burn away. None of it worked very well.

Recently, Rodney Lee, owner of Simkev Minerals, purchased an old micromount collection in which were several hirsute specimens. He was puzzling over the eternal question of removing remnants of someone's angora sweater from the good bits when he thought of combing them out. A mineral comb would be a great idea if someone could come up with one that would pass neatly between fragile crystals without causing chaos. That probably can't be done, but as he proved, one can use a comb nonetheless.

Rodney took an ordinary plastic comb, rubbed it briskly on his trouser leg for a few seconds, then passed it over the specimen. Voila! Those nasty hairs promptly jumped to the electrostatically charged comb, leaving the specimen as hairless as one could wish for.

LINERS

The difficulty with some problems (such as hairy specimens) is that the best solution may be too simple to occur to anyone. We usually go through all the complicated ones until the "Why didn't I think of that!" solution emerges.

Bill Hunt was inducted into the Micromounters Hall of Fame in 1984. He got there by being industrious, inventive, helpful, generous, and smart. He also came up with a simple solution to a long-term problem.

Bill has been micromounting for a long time. In fact, his first micromounts were made using bottle caps (inventive!). When plastic boxes came into general use in the 1950's, Bill switched to those along with everyone else. Plastic boxes brought problems, however. The most appealing mount was obviously in a black box with a clear lid, but boxes came all clear and colorless, or all black. Rich collectors bought equal quantities of each and switched lids. Well-off collectors bought black boxes and extra clear lids. The rest of us bought clear boxes and thought of ways to turn the bottoms black. We used brush-on paint, spray-on paint, sheets of black paper liners die-cut to fit, and even special tools holding scissors to allow cutting the cross-shaped liners from black construction paper. Wooden blocks were carved to fit the liners precisely in the boxes.

A lot of thought went into those liners, but they didn't always work. The boxes vary slightly in size, so there would either be protruding paper edges and crumpled bottoms on small boxes, or wide gaps in the corners of big ones.

Along came Bill Hunt. Bill didn't bother with cruciform liners. He just cut two strips of paper of the right width and length, and folded them into the box at right angles to each other. No fancy tools, no tricky corners, no paint, no die-cut sheets--no problem!

Quintin Wight

525 Fielding Drive

Ottawa, Ontario

Canada KIV 7G7

email: qwight@sympatico.ca

(1.) Personal communication, Dr. Peter Tarassoff.

(2.) The information was gleaned from Aggregates & Roadbuilding: Canada's Rock to Roads Magazine, May/June 2000, pp. 13-14.
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Author:Wight, Quintin
Publication:The Mineralogical Record
Geographic Code:1CANA
Date:Sep 1, 2001
Words:1530
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