FMF - Friends of Minerals Forum, discussion and message board

[Jordi Fabre]

The last years some unusual Calcites from an obscure locality of China (probably Chanhua in Zhejiang) came to the market. Due its shape, with a kind of thread inside the crystals, they were called "faden" as the "faden" Quartz.

Terry Huizing is a great "connoisseur" of everything related with Calcites and he kindly sent to me a warning message concerning these so called "faden" Calcites. With the gentle permission of Terry I copy below his message due its mineralogical interest.

"Hi Jordi,

The so-called "Faden" Calcites from China should NOT be called "faden", as this term applies to quartz that exhibits a thread-like, milky interior. This quartz feature is said to be caused by a slight "pulling apart" of the quartz during it's growth.

Calcites that have a central tube are all speliothems, or cave-like formations, and the growth mechanism is distinctly different than for "faden" quartz. The central tube in calcite is the channel through which the water passes as the speliothem (a helectite, or stalactite) forms. Near the end of its growth, the tube is often plugged and may not be visible at the termination. However, if you look at a broken end (opposite the termination) the hollow tube should be visible.

I hope this helps.

Terry Huizing"

[Pete Richards]

Terry Huizing is right about these calcites. I have seen many possible examples of faden calcite, but none has ever had the right characteristics of gradual extension to form the faden or thread that characterizes faden quartz. Faden crystals exist in a number of other minerals as well, and these are always alpine vein minerals ("always" is a dangerous word...). Examples include epidote, adularia, apatite, and uvite tourmaline, in my experience.

[Paul Bordovsky]

Here are a couple more pics of this type of calcite, showing the line or channel.

Paul

[Tracy]

I've got one, in my collection thread - hmmm maybe I'll try re-photographing it. :-)

- Tracy