What's the Difference Between Alexandrite and Other Color-Changing Gemstones Like Sapphire?
inOctober 27, 2011 - 4:32pm
We recently listed a stunning colour-changing sapphire ring in our Ruby Lane Shop. Within a few hours came the question: “I’ve never heard of a colour changing sapphire! Could you elaborate please? How do you know it’s a sapphire and not a huge, rare alexandrite?”
Now that’s a good question, and unless one is a gemologist or has access to the proper testing equipment, it’s not easy to answer. It’s even harder for a buyer to be sure of what he/she is buying.
It’s times like this that the internet is a godsend. We were immediately able to send the enquirer over to several links where she could read up on the differences. But since we cannot include links here in this blog, we thought it might be beneficial to list some of the key points for both buyers and sellers with the same question.
Alexandrite exhibits a green to red/purple color change and has a completely different 'make-up' chemically to sapphire. MOST color-change sapphires change from blue to purple. Finding green to red is extremely rare in sapphire, whereas that is the norm for Alexandrite.
“Several other well known gemstones, including diaspore, sapphire, garnet and spinel may also change color as a function of the light source but the color change of top alexandrites is distinctive and attractive under any light conditions.”
Spinels sometimes show a change from blue to violet but the change is usually quite weak. Only sapphires and especially garnets, show a stronger resemblance to alexandrite.
While colour-change sapphires are of 2 types i.e. blue to purple or red to green, it’s the latter that can be most easily confused with Alexandrite. These rare sapphires come from the deposit at Songea, Tanzania. However, while the red they show under incandescent light is very good, in daylight that red is muddier than that of an alexandrite.
Then, adding to the confusion are garnets, especially those from Berkily in Madagascar. But there is a difference:
“Although they look a lot like alexandrites they are different because they change color throughout the day. They are green or blue grey in the early morning and reddish in the late afternoon or in strong sunlight. Some of the stones are almost blue especially under fluorescent light but most of them are grey blue or green in daylight and change to red under incandescent or late afternoon light. The stones can show an excellent color change and can easily be confused with alexandrite.
Without gemological tests, the stones can be distinguished from alexandrites by the needle like inclusions that are common in them or by the way the stones change color according to the time of day. Although they look like alexandrites, these Bekily garnets will appear red in the afternoon while the alexandrites remain green.”
Now of course all this probably still makes it very difficult for you or me as a buyer or seller to know whether we are looking at a colour-changing spinel, sapphire, garnet or genuine alexandrite. So what answer did we give our enquirer who first posed the question “How do you know it’s a sapphire and not a huge, rare alexandrite?”
Happily, we were able to tell her that our ring comes with detailed gemological report from the AIGS in Thailand.
Why is this important to you, the reader of this blog, as a buyer? Because labs like the GIA, GRS and AIGS are highly reputable labs that run the gems through numerous tests and examinations to determine the 'species' of the gemstones brought to them. Following the testing, a detailed “gem identification report” is issued and stamped for each stone.
Diamond and gemstone rings are excellent investments ... as long as you can be sure of what you are buying. As sellers, it’s wonderful if we can provide certification for our buyers. But if we can’t, it’s worth the little time it takes to research their questions. Your customers deserve it.