BLACK STAR SAPPHIRE 7.39 ct Chantaburi, Thailand GFCO, MELIKIAN
GEMOLOGICAL REPORT № 147
Gemologist Olga Melikian | WA: https://wa.me/79990437349 21/10/2026
Telegram: @olgamelikianofficial | https://melikianjewelry.com
Weight: ……………………………..………………………….. 7.39 ct
Measurements: …………….………..…..… 13.45x11.47x4.25 mm
Сut: ……………………………………..……………. oval cabochon
Color / Color saturation: ………….. dark brown with golden sheen
Clarity: …………………….………….………….………………………
IDENTIFICATION: …………………………… Natural CORUNDUM
TRADE NAME: ……………………………BLACK STAR SAPPHIRE
Geographic Origin: …………………………… Chantaburi, Thailand
Treatment: …………………………. No indication of any treatment
Information about BLACK STAR SAPPHIRE:
The Chanthaburi mine in Thailand has already been depleted, which is why samples of good quality black star sapphires from there are especially valuable.
RESULTS OF DIAGNOSTIC METHODS
10x glass: …………..…quality very good, no cracks, no resin filling
Refractive Index: ……………………………….…….… 1.760 - 1.770
Polariscope: ………………………………..…………..………………..
Dichroscope: ………………………………….……… no pleochroism
UV fluorescence: ………….………………………… no fluorescence
Chelsea Filter: …………………………….…………………………….
Color change | Alexandrite effect (daylight | artificial light):…………
Microscope: No indication of any treatment (fillers, heating). Due to inclusions of rutile, we observe the asterism effect in this sapphire.
Special properties:
Opalescence | adularescence | iridescence ………………………No
Cats eye effect…………………………………………….……….…No
Asterism……………………………………………………………….Yes
A 6-rayed star which golden rays.
Gemologist Olga Melikian | WA: https://wa.me/79990437349 21/10/2026
Telegram: @olgamelikianofficial | https://melikianjewelry.com
Weight: ……………………………..………………………….. 7.39 ct
Measurements: …………….………..…..… 13.45x11.47x4.25 mm
Сut: ……………………………………..……………. oval cabochon
Color / Color saturation: ………….. dark brown with golden sheen
Clarity: …………………….………….………….………………………
IDENTIFICATION: …………………………… Natural CORUNDUM
TRADE NAME: ……………………………BLACK STAR SAPPHIRE
Geographic Origin: …………………………… Chantaburi, Thailand
Treatment: …………………………. No indication of any treatment
Information about BLACK STAR SAPPHIRE:
The Chanthaburi mine in Thailand has already been depleted, which is why samples of good quality black star sapphires from there are especially valuable.
RESULTS OF DIAGNOSTIC METHODS
10x glass: …………..…quality very good, no cracks, no resin filling
Refractive Index: ……………………………….…….… 1.760 - 1.770
Polariscope: ………………………………..…………..………………..
Dichroscope: ………………………………….……… no pleochroism
UV fluorescence: ………….………………………… no fluorescence
Chelsea Filter: …………………………….…………………………….
Color change | Alexandrite effect (daylight | artificial light):…………
Microscope: No indication of any treatment (fillers, heating). Due to inclusions of rutile, we observe the asterism effect in this sapphire.
Special properties:
Opalescence | adularescence | iridescence ………………………No
Cats eye effect…………………………………………….……….…No
Asterism……………………………………………………………….Yes
A 6-rayed star which golden rays.
DETAILED GEMOLOGICAL COMMENT
This 6-ray star sapphire is an interesting specimen. A star with long and thin rays, there are no inclusions that interfere with the asterism effect. The pattern with the growth zones is clearly shown. The gem report can be supplemented with data on the composition.
Considering the characteristics of this Black Star Sapphire:
Weight: ……………………………..………………………….. 7.39 ct
Сut: …………………………………………………… oval cabochon
Color / Color saturation: ………….. dark brown with golden sheen
Clarity: …………………….……………………………………………..
Geographic Origin: ……………………….…… Chantaburi, Thailand
Treatment: …………………….…..… No indication of any treatment
Recommended market value corridor (retail price) of Black Star Sapphire with 6-ray star from Chantaburi, Thailand weighing from 7 carat, no treatment as of 21.10.2026:
480-570 $ per 1 ct
Note: the recommended market value corridor in indicated on this date. The price may change over time. The value corridor is an opportunity for the buyer/ seller to get an objective assessment of the value of this stone. With the receipt of new gemological research data, the cost corridor may be revised.
This 6-ray star sapphire is an interesting specimen. A star with long and thin rays, there are no inclusions that interfere with the asterism effect. The pattern with the growth zones is clearly shown. The gem report can be supplemented with data on the composition.
Considering the characteristics of this Black Star Sapphire:
Weight: ……………………………..………………………….. 7.39 ct
Сut: …………………………………………………… oval cabochon
Color / Color saturation: ………….. dark brown with golden sheen
Clarity: …………………….……………………………………………..
Geographic Origin: ……………………….…… Chantaburi, Thailand
Treatment: …………………….…..… No indication of any treatment
Recommended market value corridor (retail price) of Black Star Sapphire with 6-ray star from Chantaburi, Thailand weighing from 7 carat, no treatment as of 21.10.2026:
480-570 $ per 1 ct
Note: the recommended market value corridor in indicated on this date. The price may change over time. The value corridor is an opportunity for the buyer/ seller to get an objective assessment of the value of this stone. With the receipt of new gemological research data, the cost corridor may be revised.