Crystal Surfaces Are Awesome!

[Sure Squintsalot]

Everybody likes to look at beautiful minerals and crystals. Their forms, colors, and textures evoke all sorts of primal wonder, analytical amazement, as well as spiritual nonsense. Crystals, however are the result of complex atom-by-atom, molecule-by-molecule growth processes governed by nano scale thermodynamic processes. Other than that manifested by the gross crystal morphology, most of these processes are invisible to us. Occasionally, it's possible to glimpse these processes frozen into a crystal surface. Unfortunately, at this point, it would take far more effort than I'm willing to determine Miller Indices for the features seen in these photos. I'm still too amazed by what I'm seeing to whip out old textbooks for deep analytics. I even forgot to record magnifaction and include a scale bar.

I used a metallurgical set-up with DIC and a lightly modified Optiphot stage to accomodate near-universal rotation of centimeter scale whole crystals mounts.

Here are recent photos of various quartz crystal terminal faces from a personal mineralogy collection built up over a few years; most were found, a few were bought, all kept, not for any obvious beauty but for their deeply interesting features:

Quartz Termination Growth Surface 01

Screenshot 2023-09-23 165118.jpg (206.14 KiB) Viewed 850 times

Quartz Termination Growth Surface 02

Screenshot 2023-09-23 165427.jpg (313.03 KiB) Viewed 850 times

Quartz Termination Growth Surface 03

Screenshot 2023-09-23 165009.jpg (227.61 KiB) Viewed 850 times

Quartz Termination Growth Surface 04

Screenshot 2023-09-23 164928.jpg (116.54 KiB) Viewed 850 times

Quartz Termination Growth Surface 05

Screenshot 2023-09-23 165817.jpg (155.86 KiB) Viewed 850 times

[Sure Squintsalot]

Most microscopes are built for viewing "2-D" subjects. As a result, there isn't a lot of room between the stage, at it's lowest point, and any given objective. Viewing something like crystal faces under DIC poses serious challenges. The faces must be roughly perpendicular to the light train, requiring that the crystal be oriented at some oddball angle, making additional demands on the already limited available clearance. Some people will inelegantly plonk their crystal in a wad of chewing gum or a rolled up booger of clay. These savages tend to be gemologists and others who look at nice things for money.

Mineralogists, structural geologists, and crystallographers have devised beautifully crafted Federov universal stages for the purpose of orienting crystals in 3-space. Unfortunately, these divinely engineered instruments are used almost exclusively for looking at crystal thin sections, measuring optical axes directions, and inputting results into stereoplots, and are useless for manipulating centimeter scale samples.

Ergo the sticky hemisphere; a simple doorknob protector (ball) with a sticky back is fitted to receiver (socket) for near-universal, stable mounting of specimens:

The Sticky Ball Universal Mount

Screenshot 2023-08-21 215934.jpg (90.67 KiB) Viewed 829 times

A first draft included some X-Y movement by way of attaching directly to the condenser stage. Here, it's used to orient tiny crystal faces of wulfenite in a hand sample:

Screenshot 2023-09-23 211145.jpg (116.69 KiB) Viewed 829 times

A few wulfenite crystal faces:

Wulfenite at 200x

Screenshot 2023-09-23 211356.jpg (59.58 KiB) Viewed 829 times

Screenshot 2023-09-23 211427.jpg (164.1 KiB) Viewed 829 times

Wulfenite at 400x

Screenshot 2023-09-23 211447.jpg (174.25 KiB) Viewed 829 times

[Sure Squintsalot]

As interesting as this kind of viewing is, epi-illuminated DIC viewing of crystals is a dynamic thing. A rotating stage really brings out wow of interference colors coming in and out of extinction. But again, more stage modifications are required; in this case a special adapter and smaller stage that could be mounted even lower that the regular stage. Then, mounting of a rotating stage plate and even a half-assed low-RPM motor to spin the whole thing:

Screenshot 2023-09-23 215800.jpg (107.12 KiB) Viewed 828 times

It's being used here to look at some slide mounted galena crystal faces:

[MichaelG.]

Very innovative … and well-worth the effort !!

Thanks for sharing the beautiful results.

MichaelG.

[Scarodactyl]

I use a very similar setup for posing my crystals for epi DIC too. Very nice pics and video! At this point you might want to start shopping for a Nikon measurescope body--you can port everything over while having plenty of Z space.
I'm not sure the gemologist/geologist mounting division described really bears out in my experience.

[Hobbyst46]

Very nice setup and images !