FMF - Friends of Minerals Forum, discussion and message board

[Bill Carson]

According to my Dana Manual of Mineralogy,: "Some adularia shows an opalescent play of colors and is called moonstone.

[Antonio Alcaide]

[Brian Jackson]

Hi
You may be interested in this twin crystal of adularia from the Alps

[Les Presmyk]

A truly interesting thread but I do have to comment on the naming of Tanzanite. In one of the issues of Mineral Digest, there is an article on Tanzanite. The thrust of the article was the inequity heaped upon Mr. Tanjeloff because he wanted the material named Tanjeloffite. He makes an impassioned argument for this honor but obviously the market preferred Tanzanite. So, someone tried to name it after themselves.

[Carles Millan]

[dtkasper]

Look under a microscope. See a certain structural shape. See the sheen. Classify it generally as adularia. The exact species is unkown without XRD. See another specimen with clay and quartz. Call is sericite. The exact kind of clay (probably illite) has to wait for XRD. There is only so much you can see in hand identification of field specimens, but that does not mean we should not use names to capture what we collect. Some are just generalizations. Of course, with the clays it appears all "mineral names" are generalizations as we get the "ideal formula", realizing the composition is highly variable. Looking at the literature, I don't see many agreeing even on ideal formulas.