OK... first the blue:



a healed fracture (fingerprint) in a..... hauyne!!! There isn't a whole lot of documentation on hauyne so it would have been guessing for everyone. Cool fingerprint as well. Really detailed in the bottom and kind of rough up top. Gubelin and Koivula tell me that a fracture started healing where the fluid droplets are smallest / the fingerprint is the most detailed.

And then the orange:

"why heated?" with that I didn't mean why would they heat it, but how can we tell it is heated

Let's get that picture into paint...



The white arrows are pointing at small inclusions that are surrounded by stress cracks aka halos. Alberto spotted them. These occur when a small crystalline inclusion expands at a greater rate then it's host when heated. The host has to give way and cracks. The top left one is best visible the bottom right one is slightly out of focus. These halo's are a giveaway for heat. BUT where that heat took place can't be told... A furnace can provide it but so can earth itself.

The blue arrow is pointing at that two phase inclusion that is surrounded by yet another massive stress crack that indicates heating.

And then the yellow arrow and the massive blob it's pointing at. My best guess is that once upon a time a large crystal was living there. Upon the heating it melted completely, the whole thing exploded thus causing that entire fingerprint it's sitting in and left the molten content partially recrystallized all over the place...

Spauwe,

This is great. A nice, gentle looksee into the world of gems. This pace I can handle.

Thanks,
Merryn.

Tim,

Very nice presentation and observations. Paint is a handy demonstration device, isn't it?

Here's a question for anybody that may know the answer. We'll assume we are talking about corundum since that is the latest subject matter.

If you have a piece of corundum with natural fractures, is it possible for the fracture to completely heal with no evidence of the fracture?

Now if this occurred in nature, I suppose it would be impossible to say. If it was done by man through heat and flux say, then you could determine this by examining the stone prior to and after the treatment process.

The reason I ask is, I considered the possibilities you outlined above and was curious if the angular fragmented inclusions above the large fingerprint and globular looking inclusion were in your estimation part of a larger inclusion at one time that "exploded" due to intense heat.

Following that train of thought and knowing that solids can't move through solids, the fragmented bits would have had to have been transported by a liquid medium or at least nutrient fed through some fluid medium to induce crystallization.

Looking at the fragmented pieces, there doesn't seem to be any evidence of healing fractures around many of them (as far as I can see in the photo.) If they formed independently of the larger inclusion after the "melt down" that would seem to make sense given their angular outlines that seem to suggest little effect from intense heat application.

Hence my initial question. Or one of them anyway. This may be covered in some book somewhere, but it would be one that I don't own.

How about the possibility that those angular inclusions just didn't melt in the intense heat? Maybe like the corundum itself, those inclusions required higher temperature to melt.

Brian, that's kind of what I'm fishin around at. It's like reconstructing an accident scene with no eye-witnesses.

if so we'll never know... Ghehehe, no seriously, I don't think so. Cracks heal cause there is a heated pressurized fluid in there that can act as a flux for the elements that will repair the crack. Remnants of those fluids always seem to be present.



I have to admit that I don't have a clue as to what they are. Very irregularly shaped solids. I strongly doubt that they have anything to do with that big exploded blob (yellow arrow). They may be of a material with a higher melting point then corundum, or may have a smaller thermal expansion rate then the other (exploded) crystals... They are not unaffected by time that's for sure.


Since we're talking cracks and their healing here's another one:



This is another sapphire that cracked somewhere down the line but this fracture didn't heal, I suggest due to a lack of fluid acting as a flux. The colours we see are caused by thin film interference caused by a substance in that crack with a significant lower RI then Al2O3: air. (I think)

Hughes has published a nice diagram on fracture healing here. The article itself is concerning related but slightly off topic matters to this discussion. Heck it's Hughes, always a good read.

Ok, I'm bored tonight.

Amber "Thing" (Fantastic Four) with sapphire eye.

Topaz cleavage, high mag.

Not my best work, but it's a non-paying job.

not your best job? You mean that amber thing with sapphire eye is not your best shot ever? I think it's brilliant

seriously though: thanks for posting, the more the better.

here's another one:



three crystals (or negative crystals?) in a spessartite from Loliondo. These garnets are full of this stuff. I'm unable to determine what it is exactly. Looks to be cubic as well. Between crossed polars they display a bit of interference colour (as seen in the image) but nothing like I know to see with anisotropic inclusions.

here it is without crossed polars:



Let's illustrate the above...



apatite in a hessonite

between crossed polars:



clearly anisotropic... very different to the reaction of the inclusion in the spess.

I got a 2x auxiliary lens for my M3Z (40x max without it) so I'm now able to get a bit more up close and personal with what I see but the lens kills my depth of field and using it for photography results in 'not so crisp' pictures...

I'm at the very bottom of the learning curve so every suggestion is welcomed warmly... the biggest reason I started this thread is to get some practise going...

John Koivula, you aren't a lurker here by any chance that wishes to take on an apprentice?

Ethical/subjective question...

Facts:
- photomicrography of gems has been lifted to a level of art by Koivula and Gubelin.
- film use still gives crisper pictures then any digital camera will take.
- digital camera's are quicker and easier when publishing on the net.
- my new 2x lens kills my depth of field but brings in desired extra mag.
- when using digital camera's one has access to SOFTWARE to enhance pictures...

Gene already pointed me towards stacking software a month ago but yesterday Keirkof showed us chatters a direct link to a great free stacking program. The software allows me to take a sharp picture of an image that I can't get sharp normally because of limitations to the depth of field. I can focus on the nearest part of the inclusion... click... quarter way... click... half way... click... 3 quarters way... click and one more at the deepest bit of it. Upload the lot, hit a button and after a few minutes of desperate rattling of my processor and some increased revs of the cooling fan a sharp picture comes rolling out. Played with it this afternoon and my focusing troubles at high mag seem to be over! Excellent! But... with all this digital magic... would it still be art?

An example... A glass filled ruby. Capturing the famous 'blue flash' with a single shot is a big pain in the behind. With the aid of this software it becomes a very easy and enjoyable enterprise... Surrounding fingerprints etc are sharp as well.



Here's a crystal inclusion with tension crack in a blue sapphire at very high mag (over 200x and then blown up digitally again), without that software there would be no way to get an image like this (even this isn't 100% sharp but give me some time, just started playing with it)



Do you consider digital photography with all it's enhancement to be as arty as shots taken with a conventional camera? What counts? The method or the result?

Hi,

You can also get interference colours from the thin film effect.

Sooner or later standard photographic films will go out of production, it's a matter of time. digital pictures will increase in definition and color results. About digital picutre enancements: when i shot a photo i tend to leave it as it is the more possible. fancy programs are great but, if you abuse of them the risk is to have an "innatural" image.
just my 2c only.
ciao
alberto

I assume you are referring to the spess inclusion from a couple of posts back? Hmmm... very possible, you mean the crystals would have a thin film of something around 'm then? Would be interesting to wack some UV radiation on there to see if there's any oil on there (it would fluoresce white then).

Can I get a reaction out of you concerning me having to disclose any photo treatments?