4
$\begingroup$

There are many great mineral specimens that occur in pockets — basically, openings in rock that may be filled with water, clay, or other soft substances that can be easily removed. Here's an example pocket of crocoite from the Red Lead mine in Adelaide, Australia. Crocoite Pocket

The problem to solve is cutting out that pocket without damaging the delicate crystals. Currently, hammer, chisels, and crowbars are used. A diamond-bladed chainsaw would be dramatically faster, but the cutting vibrations will damage the crystals.

For crystal bunches, as in the video, the miner can afford to lose a few crystals as that won't be noticeable.

In an extremely rare case (once in five or ten years of mining), there'll be a pocket found with a few extraordinarily large crystals (10 cm and up -- these are normally in the range of 3-5 cm.) These are dramatically more valuable (1,000 times more valuable. Yes, really.) but only if the crystals are not damaged.

There was one such pocket found about two years ago. Sadly, the extraction failed.

I suggested to the miner that perhaps the right thing to do was to fill the pocket with a dissolvable plastic compound to stabilize all of the crystals, use a diamond chainsaw to cut out a say 2-foot cube of rock, take it to the mineral lab, trim as desired, and then finally dissolve out the plastic.

He thought that was a great idea and asked me what should he use.

I have no idea! I looked for plastic fillers, but that goes off in the wrong direction. I suspect there's something perfect for the task in the 3M catalog, but that seems mostly aimed at the public.

So the requirements are:

  1. Low viscosity plastic stabilizing fluid that hardens to at least a firm consistency.
  2. The fluid does not introduce stress when it hardens.
  3. The fluid works over a large pressure and temperature range. (Some miners mine at 5km heights.)
  4. The hardened plastic is removable without introducing stress. E.g., by using a solvent. Note that it's fine if it takes a month or two to remove all of the plastic.

Using UV to harden the fluid is fine. I think the dental-related compounds though may not be dissolveable.

What do you think? Is this feasible at all with current plastics tech?

Note: I don't think foam will work, as I would expect the small gas-filled cells to collapse under severe vibration. But I could be wrong.

Second note: we will try out any recommendations and report back our results.

Improve this question
$\endgroup$
4
  • $\begingroup$ Just some thoughts: 1. Some specimens are extremely delicate, and flooding might physically damage them. 2. Some minerals might be attacked by the fluid, e.g., absorb or lose water of hydration. 3. The process of removing the hardened plastic also might damage the specimen. However, why not use a diamond circular saw, which would make far less impact than a chain? $\endgroup$
    – DrMoishe Pippik
    Commented Jun 7 at 1:38
  • $\begingroup$ 1. The really delicate minerals, e.g., mesolite or rutile, well you just accept breakage. Now they've been flooded in the past, otherwise they couldn't have crystallized! But I agree attempting to push in a viscous material would be a problem. That's why I asked for low viscosity. $\endgroup$
    – Walt Donovan
    Commented Jun 7 at 7:05
  • $\begingroup$ 2. Yes, agreed, so you want a non-aqueous, non-acid, and non-basic fluid. $\endgroup$
    – Walt Donovan
    Commented Jun 7 at 7:05
  • $\begingroup$ 3. The problem with using a circular saw is the depth of cut needed. With a chainsaw you can cut 3 feet deep easily. $\endgroup$
    – Walt Donovan
    Commented Jun 7 at 7:06

0

Reset to default

Browse other questions tagged or ask your own question.