Microscope for Surface Analysis

[southernlakehuronguy]

Just a suggestion. If you already own a dslr camera, you can get bellows that you could use for your inspection and photographing.

[Starguy]

@hefty
I think the standard for inspecting cabs would be 10x. A well polished cab would show zero scratches or visible defects due to cabbing under 10x magnification. It’s not that there aren’t scratches, you just can’t see them. If you increase the magnification you will see them again on high quality rock. I suppose there would be a point where the scratches are smaller than the crystalline grain of the rock.

With cabbing, most rocks seem to have a point where the polish doesn’t improve with finer grits. To my eye, this is around 14K diamond grit but I’ve seen rocks that don’t improve much beyond 1200 or even 600 grit.. Rocks like Bruneau jasper and Montana moss agate improve to 50K diamond grit maybe beyond but I’ve never tried it past 50K.

With tumbling, there is more going on than just the abrasiveness of the grit/polish. I’ve got a partially formed theory about how rocks polish in a tumbler when the polish is softer than the rocks being polished.

I think microscopy is used most for faceted rocks and rough. It allows you to focus at different depths within a transparent stone.

This is all very interesting and am looking forward to hearing about what you get. It would be really cool to see photos too.

[Starguy]

Jan 16, 2024 18:07:07 GMT -5 @hefty said:

Jan 16, 2024 16:47:18 GMT -5 Starguy said:

I’ve got a partially formed theory about how rocks polish in a tumbler when the polish is softer than the rocks being polished.

What's your theory? And what's some examples of tumbling with a polish softer than the rocks? I thought silicon carbide and aluminum oxide were harder than basically 99% of what people tumble.

Many of the oxide polishes are not hard. Tripoli is very soft and I’ve had pretty good polishes with nothing but water. My theory, (at least with agate) is that the stone surfaces kind of smear each other smooth.   Another part of the theory is that the polish makes the rock surfaces engage each other at a molecular level which makes the smearing even more effective.

[Starguy]

@hefty

It’s interesting trying to figure out how tumble polishing works. There’s definitely more going on than just simple abrasion. It’s a puzzler.

I’m looking forward to hearing what you get.  I’ve used microscopes quite a bit.  They’re amazing tools.

[ThomasT]

For what it's worth: We use an articulating arm bench mounted 3.5X-90X trinocular stereo microscope with a 10MP digital camera and powerful LEDs for looking deep into faceted stones with darkfield or for observing surfaces, minerals or metal, as well as other fabrication uses.

We also use an LED lighted hand-held digital microscope that will show surface defects scratches/chipping well beyond what can be seen with a loop and cost less than $50 and works great. 

The laptop screen images from either device are very clear and high resolution.

[iamchris]

Merely trophying last year wasn't good enough for ya, eh? 😆

Can't wait to see this year's results! May the force (magnification) be with you.

[ThomasT]

10MP rez. 144 LED cool K color dimmable under mounted ring for top surface lighting. 

On a side note: the studies you may be interested in may be satisfied somewhat with the findings of faceting studies on grit hardness and finish fineness in relation to final polish finish appearance. 

Here is an example (link below) of some data you may be trying to find... but the gemological institutes have done a lot of big studies on surface finish appearance for many years that can be found elsewhere also: 

www.attawaygems.com/NMFG/Surface_Characteristics.html

[ThomasT]

I should perhaps add that I am a believer in the old saying that 'beauty is in the eye of the beholder'. (not the eye of the equipment).

[ThomasT]

 Don't forget to let me know when you find the source of rough gemstones you can facet and "flip ...for a few thousand dollars profit".

[ThomasT]

I do believe you are correct @hefty , in that you could, as you say, ... "just add a 0 to the price and sometimes someone buys it".

Marketing seems to do the trick often enough. 

Best regards,
Thomas

[ThomasT]

@hefty I believe I fixed the link below... sorry about that.

The studies you may be interested in may be satisfied somewhat with the findings of faceting studies on grit hardness and finish fineness in relation to final polish finish appearance.

Here is an example (link below) of some data you may be trying to find... but the gemological institutes have done a lot of big studies on surface finish appearance for many years that can be found elsewhere also:

www.attawaygems.com/NMFG/Surface_Characteristics.html

[roQhound]

Jan 16, 2024 18:42:13 GMT -5 Starguy said:

Jan 16, 2024 18:07:07 GMT -5 @hefty said:

What's your theory? And what's some examples of tumbling with a polish softer than the rocks? I thought silicon carbide and aluminum oxide were harder than basically 99% of what people tumble.

Many of the oxide polishes are not hard. Tripoli is very soft and I’ve had pretty good polishes with nothing but water. My theory, (at least with agate) is that the stone surfaces kind of smear each other smooth.   Another part of the theory is that the polish makes the rock surfaces engage each other at a molecular level which makes the smearing even more effective.

The smearing you've mentioned is what I believe also. That would be true "burnishing" and I also think that happens to a certain extent when we're polishing rocks.

[Starguy]

@hefty

That sounds very interesting. I’m looking forward to seeing some photos. You definitely have the range of magnification covered.