Another Identification Challenge
Mineral Matters #442
Mineral Series. Who’d have ‘em?
It is getting increasingly more difficult to accurately, and with certainty, place a species name to a mineral.
This one is a case in point. Londonite on liddicoatite, as per the dealer label. But herein lies the problem.
Londonite forms a series with rhodizite. And liddicoatite forms a series with elbaite.
The formulas are as follows:
Londonite - (Cs,K,Rb)Al4Be4(B,Be)12O28
Rhodizite - (K,Cs)Al4Be4(B,Be)12O28
Liddicoatite - Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3(OH)
Elbaite - Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Without analysis of the specimen, there is no certainty. Without analysing the specimen in multiple places, there is no certainty. With Tourmaline Group species in particular, the actual species can change within the one crystal!
So, labels are going to get awfully big. “Londonite-rhodizite series on a liddicoatite-elbaite series, Ambalabe pegmatite, Manapa pegmatite Field, Betafo District, Vakinankaratra Region, Antananarivo Province, Madagascar”.
Below: White londonite on a liddicoatite tourmaline crystal (as labelled), Ambalabe pegmatite, Manapa pegmatite Field, Betafo District, Vakinankaratra Region, Antananarivo Province, Madagascar. Width of view 9mm. Click on the image for a higher resolution version.
Some interesting comments below,but for me if it looks like duck and smells like a duck and quacks like a duck!!!!!
I love your enthusiasm and persistence and incredible knowledge Steve, but after reading that post I thought "I GIVE UP!!!".. I've been trying to learn minerals for years now and I wonder if it is worth it for me to try to remember such detail. I have decided the answer is "no" but I can still appreciate your posts and efforts in identification and labelling.. Thank you! :-)))