7.4 Carat Fantasy Cut Color Changing Blue/Purple Umba Sapphire, 11.1x10mm
This listing is for the depicted loose gemstone that I personally precision cut on my lapidary equipment
• Massive at 7.4 carats • 11.1x10mm and 8.3mm in depth • Cut in my own dodecagonal Fantasy design with a compass cut crown • Untreated • Naturally occurring • Corundum (sapphire) • Unique attributes: Extremely rare size and clarity. This stone has some visible inclusions but it does not detract from the appearance. NO HEAT! A color shift to a medium purple/lavender is observed under warm tone spectrum lighting. Also distinct pleochroism from a dark to a light hue is observed on the tilt. Excellent clarity for material from this locality. A few photomicrographs of the most notable inclusions are included for reference.
Gemological Description: A natural untreated corundum (sapphire) with a dominant bluish violet hue, a medium tone and strong saturation. This gem has a secondary bluish green hue visible on the tilt and has a notable color shift to a violetish purple hue indoors under warmer spectrum lighting.
Photomicrograph description: This gem has some inclusions typical of corundum from the Umba Valley in Tanzania. Most notable are the fully formed rose channels that span the full length of the gem and the rutile silk lightly sprinkled throughout the gem. The crisp nature of the rutile silk is an indicator that the sapphire has not been heat treated to enhance its color or clarity. Multiple partially healed fractures are also visible off to the edge.
Gemstone Rough Country of Origin: Umba Valley, Tanzania Cutter: Sennin
Photos and videos were taken in daylight under a blue sky, direct sunlight, under my led desk lamp and under the overhead led lights in my office.