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Quench Crackled Quartz

DESCRIPTION

This image concerns quench crackled quartz, top picture is an imitation for ruby and the bottom one is an imitation for emerald.

Both gemstones were observed on microscope in immersion cell (Benzyl Benzoate) using transmitted diffused light. The picture was taken through the ocular out of loose hand. It clearly shows the advantage of an immersion cell microscope as the dye can be observed as if it was “floating” in liquid, without having the disturbance of facet edges or internal reflections of light in the gemstone.

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Lily Pad Inclusion in Peridot

This image shows a Lily Pad inclusion in peridot. One can notice that only the inclusion itself can be seen. The Lily Pad was observed on microscope without the use of immersion cell. Two very small fiber optic lights were used to only highlight the inclusion by it self. By using this technique one can avoid the hazard of internal reflections. The image was captured with a digital ocular of Kern & Sohn, which allows working in very low light conditions.

 

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Polysynthetic Twin Planes in Ruby

Provided image shows a beautiful example of “polysynthetic twin planes” in ruby. This image was taken out of the hand, through the ocular of a microscope, back in the early days of digital pocket cameras. The ruby was submersed in methylene iodide and placed between crossed polarizer’s using transmitted diffused light.

 

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Agatized Gastropods

QUESTION OF THE WEEK

WHAT IS THIS?

 

CATEGORY: Travel and Prospecting

 Traveling to remote places for prospecting purposes can often be disappointing, certainly when not having prior knowledge of the location. Searching for agatized gastropods on unknown locations was certainly not easy, as they lay on or just below the surface scattered around between millions of other stones and minerals.

Morocco and in particular the Western Sahara, has endless rough-edged cliffs eroding down the Atlantic Ocean and somewhere along those cliffs is the home to these beautifully and well-formed agatized gastropods that can be seen on the pictures above.

After several days of walking, I spotted the first agatized bivalvia, which provided me enough energy to continue walking for two more weeks over this dry and bare landscape in search for some gastropods. All the effort was eventually rewarded with these beautiful samples. There are some to be found, but few and far in between when you are looking for some quality.

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Unidentified Inclusion in Emerald

QUESTION OF THE WEEK

WHAT IS THIS?

CATEGORY: Unsolved Case Studies

LEVEL: Difficult

PURPOSE: Research

DESCRIPTION

The concerning emerald ought to be coming from Chivor mine in Colombia. It concerns a rough crystal with one unknown inclusion and one unusual three-phase inclusion. The picture shows 4 different images, all photographed perpendicular to the optical axis of this emerald.

OBSERVATIONS

Fig. (1 and 2) By observing the “unidentified” inclusion (0,1mm x 0,17mm) on microscope between crossed polarizer’s with ¼ lambda retardation plate, using transmitted diffused light without immersion, it shows the presence of an inclusion with attribution similar to a zircon inclusion in corundum. There is one more inclusion like this, with the same character, but is difficult to observe even with the use of immersion cell due to its depth in the crystal.

Fig. (3) The same unknown inclusion observed in the same direction, using only diffused transmitted light. This time no polarizer’s or retardation plates were used, but observed on microscope in immersion cell.

Fig. (4) This three-phase inclusion shows an unusual phenomenon. Red arrow points out to the solid phase/crystal, which shows again an inclusion. The cubic crystal (Halite?) itself measures (0,05mm x 0,05mm).

CONCLUSION

  • The first inclusion (Fig 1,2 & 3) remains until now (29-7-2018) unidentified. The general question being: could this be a ZIRCON inclusion, as this would be rare? To my concern, it’s important that it can be visually identified.
  • How would this three-phase inclusion (Fig 4) be defined and what is the inner inclusion in this crystal (a negative crystal, a fluid inclusion or another?).

The reason for this post is to share this image amongst other gemologist all around the world to share their knowledge in order to resolve this matter. As a gemologist I understand that it is hard to impossible to diagnose a gemstone/inclusion without researching it yourself, but the possibility remains that this inclusion is diagnostic to a colleague gemologist somewhere in the world.

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Sandmeier-Plato Striations/Lines

Welcome to Case Studies

QUESTION OF THE WEEK

WHAT IS THIS?

 

 

 

 

 

CATEGORY: Mounted Gemstones

LEVEL: Medium to Difficult

PURPOSE: Recycling

DESCRIPTION

This ring was sold by an auction house. The gemstone mounted in the ring was described as being a “colored center stone” mounted on an 18 karat golden ring. The item was bought to be recycled.

OBSERVATIONS

This pink transparent center “gemstone” mounted on a ring doesn’t show any external abnormalities. It is a facetted gemstone. Through examination in immersion polariscope with ¼ lambda retardation plate, it visually reveals the gemstone being uniaxial. In normal cases, it’s fairly easy to determine the optic sign with the retardation plate, but in this case due to the surrounding alloy, it is not visible. Therefore, the optic sign has to be determined through refractometer readings. By usage of the gemological refractometer, results show to have following readings: ne = 1,760 and no= 1,768 with a birefringence of 0,008. As the HIGH RI is constant, it proves that the gemstone is uniaxial (-1). By observing the gemstone through dichroscope, a mild dichroism can be noticed by manner of the colors being yellow and pink. Under UVL, the center gemstone shows a strong red fluorescence and a strong blue fluorescence under UVS.

It was not possible to verify the specific gravity/density since this gemstone is mounted in a ring. Both side stones tested negative with the diamond tester. No further research on them was requested.

Gold was tested with a conventional acid test and shows to be 18 karat.

During the first microscopic observation between crossed polarisers (without immersion liquid) in the direction of the optical axis, it showed that this stone has Sandmeier-Plato striations/lines.

Secondly, the mounted gemstone was submerged in immersion liquid and observed again on microscope using, shadowing filter, transmitted and oblique light. It revealed that this gemstone has no gas bubbles and no sign of bend growth lines.

RESULT

It is an 18 karat golden ring containing two diamond imitations with a central gemstone being a pink synthetic sapphire.

CONCLUSION

It is rather difficult to observe Sandmeier-Plato striations/lines in gemstones mounted in jewelry without the use of immersion liquid. In this case they were clearly visible without the use of immersion liquid. Observing them can be very important in light colored corundum (e.g. colorless, light yellow and light pink sapphires) to separate them from their synthetic counterparts. In synthetic ruby and blue sapphires made through flame fusion, gas bubbles and bend growth lines are to be expected. When those features are absent in very clear stones, Sandmeier-Plato striations/lines would be very indicative dealing with synthetic corundum made through flame fusion procedure. When a strong UVS (blue) and UVL (red) fluorescence is present the Sandmeier-Plato striations/lines and fluorescence would both become diagnostic features.