Mogok Sapphire

Polynesian sapphire

Over the past five years, fine Burmese blue sapphires from the Baw Mar area of Mogok have reached the market. Sapphire from the Baw Mar Mine in Mogok Over the past five years, delicate Myanmar blu ishires from the Baw Mar region of Mogok have entered the marke. Facetted rocks show typical pronounced green to violet plochroism when seen perpendicularly or parallelly to the carbon line, with moderate to high levels of satiety and moderate to deep-toned.

The majority of specimens were relatively pure under the scope and showed several twins with white acicular pockets (probably boehmite) at the intersection points. Often these entrapments were associated with cracks. Pins, probably rutil, were found only sporadically, but small blood plates and acicular particulates, probably islenite, were found more infrequently.

The majority of the rocks contain open and cured cracks near the surfaces, but also crystals of K-feldspar and glimmer (identified by Raman) were not uncommon. Saphires also had a relatively high ferrous composition, little galllium and very little Titan. The FTIR spectrum of the UV-Vis-NIR spectrum showed intensive ferrous absorbance, and the FTIR spectrum showed mainly boehmite and micaceous tapes.

The sapphire of Baw Mar, in most cases, can be differentiated from the sapphire of other locations on the basis of meticulous microscopical observation in combination with spectroscopical and analytical chemistry. Myanmar blues have been valued in the precious stone industry for several hundred years. Practically all of Burma's precious stone grade bluestone ( "Myanmar") has been found in debris along the Mogok Stone Tract.

Saphires described above were found mainly in the Kyat Pyin area near Kyauk-Pyat-That, Kabaing and Thurein-Taung (all western of Mogok) and near Chaung Gyee in the northern part of Mogok (Gübelin and Koivula, 1986; Kiefert, 1987; Hughes, 1997; Themelis, 2008; Smith, 2010). Over the past five years, bluish rhododendrons with characteristics different from those of "classic" Myanmar rhododendrons, allegedly from the Baw Mar region of Mogok, have entered the sapphire markets (Figure 1).

Illustration 2. On this Mogok Stone Tract geologic chart, the red arrows mark the Baw Mar Mine area. Baw Mar is located in Kyat Pyin, just north of Mogok Town ('Figure 2'). Sapphire from small businesses used to be of inferior value here in the past.

It is only since 2008 that large quantities of precious stone grade blues are manufactured here. At the end of 2012, one of the writers paid a visit to Mogok to gather bricks directly from Baw Mar and other landmines for the Gübelin Ge lab (GGL) project. Following the recent opening of Mogok to non-nationals, a large group of GGL employees returned to the area in July 2013 to get a better idea of the situa-tion and gather extra sampling directly from the well.

During August, November and December 2013 another writer visited Mogok and the Baw Mar mine and watched the dramatic changes. A brief review of the Baw Mar area's topography, description of current extraction techniques and the micro scopic, chemistry and spectral properties of it.

Baw Mar is located in the northwestern Kyat Pyin municipality, 12 leagues westwards of Mogok, at 22°54?. The area has a similar complexity to the Mogok Stone Tract (Figure 2). Non-sapphire-containing leuco granite dykes and granite bouldering pegmatites penetrate weather-beaten cornice, which can be seen at groundwater levels in the rock faces at risk (Fig. 3).

Out of this synenite, which has penetrated weather-beaten cornice like the megmatite, the high-quality sapphire is extracted, as well as from bags that have developed on the uncovered leuco granite. The last Sapphire are imbedded in a ceramic lens (feldspar converted into kaolinite) and encircled by bio-tite glimmer and chloride (Figure 4).

Illustration 3. Illustration 4. Sapphire containing loam bag in a heavily crumbled and breccia area. Baw Mar Mine (Fig. 5), with its own grading and slitting equipment and large scale machines, is a more effective manufacturer than other privately owned companies in the Mogok area. Baw Mar Mine combined open cast mine and tunnel construction as shown in Fig. 5 (above).

An excavated 10-20 -metre long stratum is excavated by dozers and diggers (Fig. 6, left). Afterwards, the grit is conveyed to the car wash by means of irrigation system (Fig. 6, right). Illustration 5. The wells were shut down in November 2013 and the rocks were largely excavated in order to achieve lower sapphire contents.

Illustration 6. Gravel is conveyed with poured out of the tubes to the car wash. When the tunnel ends, which can be as deep as 80 metres (Figure 7), the colliers use a bit to make small openings in the wall of the cliff and then break the weather-beaten rocks between the openings with a pneumatic hammer to gather the materials.

Lifting the product to the top and transporting it to the car wash. The pebbles containing precious stones are packaged in the car wash (Fig. 8 ) and conveyed to the grading system, where the precious stones containing saphire are graded with screens of different width. Saphires are then ground and burnished on site (Fig. 9).

Sapphire glossy sapphire is up to 15 ct. in all. Illustration 7. Illustration 8. Gemstone pebbles are collected in this wash facility and filled into barrels. Illustration 9. Baw Mar Sapphire is available in different dimensions and grades for bevelling. Preforms of sapphire from Baw Mar. In the first trial, 30 non-heated and facetted bluish saphires with a height of 0.20 to 1.63 ct were analysed (Table 1).

The facetted specimens were given to one of the writers directly from the colliers at the well. Further specimens, among them two facetted saphires ( "SABUM284" and "SABUM285"), a 7th 32 ct cabin (SABUM282) and a coarse sapphire section, were taken from the mine to confirm the original dates. Raw materials were taken directly from the car wash by the writers.

Finally, four coarse saphires were used in this trial and ranged from 0.16 to 0.84 ct (SABUM286_1, SABUM286_2, SABUM286_3 and SABUM287). For the observation of the long and shorter wavelength ultraviolet fluorescent reaction of the specimens (6W bulbs at 365 and 254 nm respectively) and for the measurement of refraction index, double refraction and pneochroism were used.

12 specimens were analysed by means of inductive linked beam lasers (LA-ICP-MS). For each specimen, a group of three individual point analysis (120 ?m diameter) was gathered at a 10 Hz pulse rate and a 50 second laser power ablation period of 6.2 J/cm2. Polarised absorbance spectrums in the 200-1500 nm region were captured with a Cary 5000 ultraviolet/visible/near infra-red (UV-Vis-NIR) spread spectrum analyzer with infra-red polarisers.

Between 6000 and 400 cm-1 with a Varian 640 FT IR spectrum analyzer with 4 cm-1 dissolution and 64 scan (the backgrounds were recorded with the same parameters). The Renishaw Raman System 1000 has been used in combination with a Leica Spectroscope for the characterization of available enclosures.

Non-polarized and non-oriented spectrums were acquired with 514 nm AR at 10 mW in normal operation (20x magnification), from 200 to 2000 cm-1 (three sweeps with a 30 second capture time) at approximately 1.5 cm-1 resol. Illustration 10. Illustration 11. Pins, presumably Böhmite, connected with stress cracks at the point of junction of the dual plane in SYBUM163.

The majority of the specimens were pleochroitic, from green to violet shades, with moderate to high levels of satiety and moderate to deep tones. Except for the less unsaturated sapphire, the specimens showed their deep-red pleochrome colour along the C-axis (o-ray). The specimens were all inertial to long- and short-wave ultraviolet rays.

Illustration 12. Illustration 13. Microscopical observations showed that the specimens were relatively free of entrapments and sometimes showed occasional pronounced poly-synthetic twins (as in Fig. 10) in two or three direction parallelly to the diamondhedral surface {1011}. Gemini formation is connected to the intersection of two levels of twins or in three almost vertical orientations, if there were three levels of twins, often connected with small cracks along these "needles" (Figure 11).

In addition, even colour zonings were seen; cured cracks composed of thin minuscule crystal as shown in Fig. 12; thin reflecting plates (Fig. 13); darkish, uneven pins, as shown in Fig. 14 and 15, which are probably ilmenites; and seldom a few brief pins shown in Fig. 15, which are most likely rutiles.

Rarely crystalline inclusion has been seen; the specimen SABUM285 shown in Fig. 16 is one such example. Specimens often showed both reflecting open cracks and open cracks with epoxy resin, as shown in Fig. 17. In contrast to the mogoksapphes described in the past, where ruptured pins and crystalline pockets such as zirconium, avatite, plagioclas and sphogopite glimmer are common (Gübelin and Koivula, 1986; Kiefert, 1987; Hughes, 1997; Themelis, 2008; Smith, 2010), only a few specimens of Baw Mar contain brief ruptured pins and crystals pockets.

Raman spektroscopy was used to identify these pockets as glimmer and K-feldspar (cf. Tlili et al., 1989 and Freeman et al., 2008). Illustration 14. Illustration 15. Shorts, probably rutil, and some uneven pins, probably islenite, in SABUM 166. CADXRF chemistry of the main and secondary element of 30 specimens yielded Fe between 1000 and 6800 parts per million, with an intersection of 4400 parts per million.

Ti levels were relatively low, from below the EDXRF detectability threshold (in nine samples) to 140 parts per million, with an intersection of 30 parts per million. LA ICP MS analyses of 12 specimens yielded 57Fe from 900 to 4500ppm, 71Ga from 35 to 115ppm, 49Ti from 15 to 115ppm, 25Mg from 5 to 80ppm and 51V from 0.5 to 50ppm.

Ga/Mg was used to distinguish between different types of geologic sapphire. The Ga/Mg rate within the specimens examined ranged between 0.6 and 17, confirming the complex geologic origins of the region's sapphire stains. Illustration 16. SABUM285, by Raman spyroscopy.

Illustration 17. Fig. 18 shows polarised UV-Vis-NIR spectrums in the 250-1000 nm region for the specimen type PABUM282. The majority of other specimens showed very similar spectral characteristics. We watched the Fe3+-related set of ribbons in the purple and turquoise spectral ranges between 370 and 490 nm, which had a relatively high level of intensities (Ferguson and Fielding, 1971; Eigenmann et al., 1972; Schmetzer, 1987).

Bigger specimens showed a cut-off at about 340 nm, as the ferrous property there has satiated the spectral photometer detection due to the longer light-transmission. Both specimens showed similar spectral characteristics. In contrast to the classical Myanmar sapphire, Baw Mar specimens contain high Fe3+ ultraviolet visual absorbance tips in purple and blues; most also show an intensive bead at ~340 nm, as shown in Fig. 19 (Hänni, 1994).

In the near infra-red range, the intensities of the Fe2+/Fe3+ ribbons are very different and can in some cases be confused with the basalt sapphire spectrum (Kiefert, 1987) the near infrared), and with less intensive ribbons (in green) by Fe+2+/ Ti+4 couples. by 0.1 absorption unit for clearness. to one mils.

probably due to water-containing minerals such as glimmer and boehmite (Smith, 1995; Beran and Rossman, 2006). Much of the rehearsals we examined showed no groups in this area, and K-Feldspat. Mogok Baw Mar mine blues showed significantly different characteristics to Mogok "classic" blues.

Baw-Mar specimens, consisting of syenit which has penetrated weather-beaten cornice and bags that have been deposited on leucogranit, are usually green to violet-blue in colour. These are often free of entrapments, sometimes with twins in several axes and pins (most likely boehmite) at the intersection points of the twins flat.

It also shows small blood plates, cracks cured and open, uneven pins that are most likely ilmenites, and occasionally small pins that are probably rutiles. Only a few crystalline entrapments were detected as K-feldspar and glimmer by means of micro-Raman analyses. The spectrums of UV-Vis-NIR differ from the inclusion of classical mogok stones with high iron-related ribbons, so that they are sometimes mistaken for basalt coloured bluish saphires.

Further research is ongoing on the Baw Mar geologic formations, as well as classical Myanmar blues and similar materials from other mining sites around the world. The research will provide further insights into the affirmative sample discovery from this mine and improve our knowledge of the difference seen in sapphire from other locations.

To the Mogok community for their leadership and positive critique in this area. Faerguson J., Fielding P.E. (1971) The origin of the colors of naturally occurring saphire. Koivula J.I. (1986) Photo Atlas of Inclusions in Gemstones, Opinio Verlag, Basel, Switzerland, 532 p.

and sapphire by Hughes R.W. (1997) Ruby & Sapphire. Mogok Stone Tract, Burma - Geoology and gems. Kieferert L. (1987) Mineralogy studies on the characterisation and distinction of saccharides from nature and synthetics. The Mogok Stone Tract eruptive rocks: their dispersal, petrographic, petrochemical, sequencing, geo-chronology and economical-geological.

A new geochemistry instrument to distinguish between magnetic and metamorphous sapphire with a Ga/Mg ratio: Peucat J.-J., Ruffault P., Fritsch E., Simonet C., Lasnier B. (2007). In this article, Smith C.P. (1995) contributes to the comprehension of the infra-red spectrum of ruby from Mong Hsu Myanmar. of Saphiren ("Sapphires", 2010). Gémelis T. (2008) Gem and Mines of Mogok.

Mehr zum Thema