Hello,Id like a little help differentiating between silk and growth lines in corundum.Theoretically I do understand,but under a microscope its pretty confusing.Posting pics of the stone under a microscope,The inclusions seemed pretty angular.*
Hi Nirmala,
The images seem to be focused on the stone’s surface showing what looks like typical cutting/polish grooves that intersect at the facet edges (very angular). I do not see anything that looks like silk or growth lines, which when present, would optically transition through facet edges.
Cheers!
4 Likes
You have a very good image of some silk-like inclusions in IMG_4916 
These are the patches of hash-mark lines running at an oblique angle from the facet groove-lines.
In IMG_4918, it appears to be a healed fracture, but the edge on right side terminates at the adjoining facet edge. This could be an optical illusion. It is not easy to determine if that is internal or a surface blemish. For the most part, it does look like a healed inclusion, but normally those will have more of a curved line pattern (fingerprint) than the linear lines here.
Could be negative crystals or seed crystals that were exposed to a thermal treatment ???
Cheers!
The last two pics are from the net…not mine its for reference…i thought the long parallel lines were silk like in corundum from burma or srilanka.But i never thought of polishing lines…
Hi Nirmala,
Thanks for clarifying the source of the two prior images.
The three images you recently posted have really good detail! 
But they don’t seem to show typical silk inclusions. They look more like strands of “rain drops”, which is a common indicator of flux grown material.
Here are two reference images from Lotus: Raindrop strands A, Raindrop strands B
1 Like
thank you for replying.this is a certified ruby i got online.im worried now if it’s synthetic…let me try better pictures…im interested in collecting and am trying to learn more…nowadays stones are not sealed by labs.i don’t understand why.They should seal the stones they certify.otherwise i dont see the point in certified stones…
I have been collecting stones as well. Unfortunately, I have come across a few “questionable” vendors and have already challenged two of them regarding the accuracy of the “certification” or species.
One was very open to the stone being returned with a refund and the other never responded back to me. I decided to keep the first one without returning it or refund, because it would most-likely be resold “as-is”. I am more inclined to keep the stone off the market. It came with a very basic “certification” envelope with a stone window (unsealed) and well… not very accurately described either.
Did the certification you received indicate any treatments, such as heat? I am not 100% sure your stone is lab grown or a simulant a few images cannot determine that. There are always exceptions to the rules, it seems.
I would verify as much of the basic gemology data points as I could, to see if the stone certification has any inaccuracies. Can you measure the RI, SG and other test points, such as using a Polariscope and Spectrometer?
Is this one of the stones you had posted about in February or is this a new one? I seem to recall you had a UV light from that post. How does this stone behave under UV?
Another point of interest is how the facet edges on this stone seem rough and not very sharp. @beargems had indicated that could be another common indicator for lab-grown material.
.
Cheers!
even i have been buying quite a lot of stones ,rubies emeralds alexandrites and sapphires.once after paying the seller refused to send it wanting more money…and another sent a parcel with no stone in it but claiming he packed it…There are very honest people too…I have randomly been photographing inclusions to learn more.These pictures are from one of the rubies …Let me figure out which one and post a pic with the report.I also feel these gold reports are very misleading.When it says a lotus gold report i expect a stone good stone taking in the reputation of the lab and the word gold report also just makes u go for the stone…But the id is right but its not a great stone…not upto whats called gold report…So now i realise its just a normal report identifying the stone.it has nothing to do with the quality.
There is an indicator for possible synthetics called “chattering”. These interruptions are seen on facet faces, not at facet junctions. Facet edges (junctions) can be worn or chipped on any gemstone (including diamond).
For common diagnostic features in synthetic corundum look for curved striae features within. Other strong indicators of synthetic corundum are air bubbles. Bubbles can also show up in lead glass treated hybrid rubies and sapphires.
2 Likes
Can you pleas post pics of the whole stone? It’s hard for me to get a sense of what you have there with just the closeups.
1 Like
This is almost certainly not silk nor growth lines.
1 Like
There are only a few labs that are absolutely trustworthy. It’s easier said than done but if you stick to GIA, AGL, GRS, and Gubelin (I may be missing one or two) you will almost certainly be guaranteed to know for sure what you are buying. There are myriad gem labs that “certify” gemstones that are either not natural, or they are natural but they are not calling out treatments.
I have seen countless examples of the following materials “certified” as “natural” from bad acting gem labs:
- Quenchcrackled and died quartz (usually in red, blue, or green sold as ruby, sapphire, or emerald)
- Synthetic corundum (flame fusion and flux grown) sold as natural ruby and sapphire.
- Glass filled (composite) Ruby sold as “natural ruby” (while failing to disclose the lead glass filling)
- Beryllium diffused corundum sold as natural sapphire and Ruby, again failing to disclose the diffusion treatment and “certifying” the goods as “natural.”
With these disreputable gem labs many times the issue is not misidentification of the material - it is the lack of disclosure/identification of treatments. This is just as, if not more, harmful than misidentification of the material.
3 Likes
It’s a very nice stone, and it seems to me that if it were synthetic, the very minor (and to my eyes, non-significant) blemishes (tiny breaks in facet lines, very minor surface level inconsistencies), would not exist; that is, the synthetic stones I have seen lack many of these natural quirks of a ruby, they often look too good to be true, which usually means they are not true, per se.
This is probably something a lot of people would disagree with, but I think it’s largely moot to worry about whether a stone is natural or has been treated. Take a look at some of the links to the texts I included in the posting related to geological theory and you will quickly see that gemstones have been treated in many ways since the dawn of at least the ancient textual record. Many such treatments were highly refined, and given that gemstones are amongst the most durable things humans have ever taken an interest in, and have been continually coveted, and hence preserved, since the dawn of time (often reworked, you may be surprised at how many ancient stones are reworked and resold in modern times), it very hard to say what was treated when and how. Yes, chemical analysis can reveal a lot of the ‘what’, but but the ‘when’, and I have several ancient treated stones that I greatly appreciate, treatments and all.
Sorry for the rambling reply, but you said you are concerned that it’s synthetic, which I can imagine is concerning and worth determining, but i really love the pics, it’s a darn nice looking stone, so if the price was right and if it’s real, i personally would be super happy with it.
1 Like
curved striae, often with color banding and especially bubbles, along with inclusions of unmelted aluminum oxide are hallmarks of the verneuil process…oldest and cheapest method of making synthetic corundum stone.
The easy question is how much does it weigh and what did you pay for it. That’s the very simple way to get an idea of manmade or natural. Over 90 percent of the sapphires and rubies are treated since the 90s. I’m not against treatment but only the largest and most perfect stones are not treated in some manner due to the value of the large almost perfect stone where treatment would devalue it. Also like a previous poster stated there are only a handful of labs that are basically honest and very adept at certified standards. There are very very few real deals in gemstones. The average cutter or collector will never have the opportunity to see much less purchase the ten percent of the stones that are real and untreated.
Similar to you or myself trying to buy uncut high quality diamonds. We will never ever get the chance to see the rough much less purchase it. Just my opinion after playing the game for a long time.
1 Like
Gemstones are certainly confusing. I think I need to invest in a good microscope first and do a short course. Please do give me some suggestions for a microscope, the ones I use are not professional. Thank you so much for clearing out the confusion. I think I just got one small 1 carat alexandrite that was sealed . All the other stones were not sealed .
I bought my microscope from eBay and added a dark stage from a cheap broken microscope I found on eBay. My microscope is a bousch and lomb but I also have an American optical one and a Gemoro that I took the dark field stage from. They all work but the Bausch and lomb is the nicest and best. I also have a range of eye pieces depending on what I’m doing. And a great stand that works with all of them. You don’t need an expensive one. Just something that can go to 60x and the most important part is the stage. Gem microscopes are highly over priced. A binocular style is the best and you can remove one eyepiece and put a camera in that spot when you need to take pictures. There are some that have a third spot to put a camera permanently. The band l scope is a.7x-3x and I have eyepieces from 5 to 40 so it goes from 3x total to 120x total. I think I have about 300 in the best one completely.
1 Like
Thank you will look into it.