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Tsarstone collectors guide

Alexandrite guide forums

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Does the color-change behaviour known as the Usambara Effect have any relations to the Alexandrite Effect?
Usambara effect suggested by the Mineralogical Museum of Oslo after Usambara Mountains of Tanzania, where Norwegian geologist Asbjorn Halvorsen collected chromiferous green tourmaline which displayed strong color change effect. The Usambara effect describes a color change dependant not on the type of illumination as with the Alexandrite effect, but rather on a change of path length of light through the gemstone in a single orientation.

With Alexandrite Effect, if the illumination is stronger in the red wavelengths as with candle light, red becomes the perceived color. In daylight which is stronger in the green wavelengths to which the eye is much more sensitive, the perceived color is green. With Usambara Effect, once the thickness of the gemstone reaches a critical point, dependant on concentration of the elements chromium and vanadium, the perceived color of the transmitted light shifts from green to red. Which explains how Usambara effect was discovered in the first place: gem quality tourmalines from the Umba Valley (Tanzania), each green by transmitted light, when placed on top of one another, showed yellow color, succeeded by orange and red as the thickness of the gemstone pile increased.

Does the famous Tavernier diamond with it substantial color change between incandescent light and daylight show the alexandrite effect?
The Tavernier diamond, also known as the Blue Diamond of the Crown or French Blue, is a Type IIb diamond with high levels of boron impurities. The absorption spectrum of boron causes these diamonds to absorb red, orange and yellow light making Type IIb diamonds appear bluish or greyish colors.

Color change in the Tavernier diamond could be actually the Purkinje effect, where in bright light the human eye is more sensitive to red and in dim light the eye is more sensitive to blue-violet light, which causes the color of bluish gemstones to slightly enhance in dim lighting.
Topic page 1 of 1
Methods of Producing Synthetic Alexandrite
Manufacturer found a way to synthetically create Alexandrite
The Alexandrite Laser
Alexandite Questions and Answers
Alexandrite Frequently Asked Questions
Alexandrite buyer's guide. Chapter 9, Alexandrite gemstone buyer and collectors guide.
My grandmothers alexandrite favorite ring
My Grandmother left me her favorite
What is the difference between chrysoberyl and alexandrite?
Chrysoberyl is the species name and Alexandrite is the variety name. Alexandrite is that variety of chrysoberyl that changes color as a function of the light source; green in daylight and red under incandescent light.
Is there a difference between Russian and Brazilian Alexandrite gemstones?
The mining of alexandrite in Russia lasted less than 100 years from the time it was discovered in 1833 to the early 1900’s. It was George Kunz, the gemologist/gemstone buyer for Tiffany & Co that probably did the most to popularize this unique gemst
Definition of Alexandrine
A misleading term for synthetic alexandrite-like sapphire, which changes color. Also called synthetic alexandrite.
Alexandrite Myths, Legends and Lore
Collection of myths, legends and lore surrounding the alexandrite gemstone
Alexandrite Synthetics and Imitations
Guide to synthetic alexandrite production, alexandrite imitations and the differences between natural and synthetic alexandrite
Synthetic alexandrite identification
Some modern synthetic gemstones look more natural and are more difficult to identify, but an experienced jeweler or gemologist can usually classify them
Alexandrite World Occurrences
Study of all the known historical and confirmed alexandrite deposits and mining operations
What is the june gemstone?
What is the june gemstone - alexandrite, pearl or moonstone?
Are there any other gemstones which change color?
How do alexandrite and color change garnet differ in appearance?
Chrysoberyl Species and Variety
Information about the chrysoberyl mineral, it's properties, varieties and history
Definition of Alexandrite cat's eye
A chatoyant variety of alexandrite, with parallel inclusions. Cut en cabochon, it has a light cat's-eye effects.
Chronological History of Alexandrite
Chronological history timeline, depicting the history of the alexandrite gemstone and it’s roots
Book Announcement: Russian Alexandrites by Karl Schmetzer
Russian Alexandrites is illustrated with more than 200 colour figures and photographs, addresses mineralogists, gemmologists, historians, mineral and gem collectors as well as all members of the gem trade.
Book Announcement: Russian Alexandrites by Karl Schmetzer
Russian Alexandrites is illustrated with more than 200 colour figures and photographs, addresses mineralogists, gemmologists, historians, mineral and gem collectors as well as all members of the gem trade.
New Book: Russian Alexandrites by Dr. Karl Schmetzer
I am sure everyone will be interested in this. I have just received a review copy of Russian Alexandrites and will be posting a review on...
need advice as quickly as possible
My home burned completely. I lost two Alexandrite rings. I lived in Turkey in 1962. My father was an officer and bought from a very...
re: advice
I have the destroyed ring. the stone measure 14mm
Deciding Between Natural and Synthetic Alexandrite
Hello Everyone, My boyfriend (soon to be fiancee) and I are looking at getting an Alexandrite as the stone for our engagement ring. We are...
How much will a typical one carat alexandrite gemstone cost?
The retail replacement cost for a 1ct. alexandrite could be anywhere between $500 to $12,000 per carat. The intensity of the color change and the attractiveness of the colors are the most important factors in determining the value of an alexandrite. With
Is alexandrite the most expensive gemstone in the world?
Along with diamonds, rubies, and emeralds, top quality alexandrites are among the most expensive gemstones in the world. In larger sizes over 4.00 or 5.00cts., Burmese rubies are more rare and expensive than alexandrites but in sizes below 1.00cts., alexa


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