FMF - Friends of Minerals Forum, discussion and message board

[Roger Warin]

Hello,
This is an unusual mineral for the simple reason that it is only composed of boron without silicon.
A window opened in my border freeing my imagination...
It is nifontovite, an oxoborate (not a borate) of Ca.
I really like my photo.
And you, what do you say about nifontovite?

[Bob Morgan]

Interesting indeed and quite a photo.
The small, attached crystal shows all the signs of being a twin. In particular the light growth shadow in the main crystal. It's slightly offset due to refraction.

[Peter Megaw]

Interesting species from an interesting skarn system dominated by boron silicates...danburite probably comprises 80% of the gangue. The abundance of boron at Charcas may indicate that there are borates at depth in the carbonate section that hosts the deposit.

Jean de Rivieres has an exceptional manuscript on Charcas pending publication in Mineralogical Record. One key take away from his study is that the workings are all interconnected and that most of the mine attributions you see for specimens from there are wrong...or if they are right it is the luck of the draw. However, it does appear that most...if not all...the nifontovites are from the Rey y Reina Mine.

Nifontovite occurs with a few other paragenetically late non-silicate boron species including borcarite and cahnite (the latter two just found last year). I suspect there are more to be found to open Roger's window further.

A few nifontovite crystals to 7 cm were found at Charcas prior to 2008 when a small find was made of a few hundred crystals...mostly sharp 1-3 cm limpid colorless singles. These gorgeous crystals show a wide variety of terminations...and based on Bob's comments I'm guessing twinning is more prevalent than indicated by the literature. This find was followed in 2009 by a larger find of more acicular crystals, many included with the bakerite variety of datolite. Many of these were large (5-20 cm) matted aggregates of crystals to 8 cm long...mostly with an unappealing matte luster. Single crystals shed from these mats were abundant.

This year things changed again for the species when a large vug (perhaps 1.5m deep) was found lined with splendent limpid crystals to 15 cm long...again mostly in flat jack-straw masses to 30cm across. A few hedgehog groups of free-standing crystals were included in the find...two shots of one of these are attached. Arguably this find resets the bar for nifontovite.

[Roger Warin]

Hello Bob,
I think you are absolutely right. It must be a twin. Pete, help us.
My age, almost 90, gives me immense joy: we are no longer afraid of proposing “crazy” hypotheses when they seem very real to us.
Every time I ask ChatGPT a question, it answers me like a beginner student.
This means that I am still borderline, or close to the asylum…

[Roger Warin]

Hello Peter,
I am happy to benefit from your experience. You already helped me with a colemanite.
Can I ask a question?
The deposit has dimensions of between 500 and 1000 m?

My specimen was purchased in Munich in October 2013.
Is it possible to find good quality finished crystals for taking photos.
Is the presence of streaks in my crystal an exception or, on the contrary, are streaks common?
Thank you.

[Linus]

Tired of looking at those skinny clear nifontovites? For the size freaks out there, here's one of the plumpest single nifontovites Ive seen (single crystal near center right edge on the photo), 0.5" across! This entire plate is nifontovite.

[Peter Megaw]

Roger...The Charcas skarns are a series of "scabs" plastered on the sides of an intrusion about 1.5 km in diameter. They wrap around about half of its circumference but are not continuous. There are also veins that cut the skarn and intrusion. They seem to keep finding more orebodies farther to the east and west, so if you unwrap them they aggregate probably well over 6 km in length. Mining has proceeded from the surface to over a km and drilling shows mineralization remains open to depth.

If you got your piece in Munich in 2013 you almost certainly got it from Mattias Jurgeit, a German geologist and mineral dealer who got a major portion of the 2009 find when he was working in Durango. I bought his collection in 2015 and he had several flats of nifontovites.

There are a number of examples form the 2009 find in dealer stocks that are image worthy. I have not seen many singles from the recent find, but they must be out there as the specimens tend to shed a bit. I will try to shoot some of my singles when I get home.

I'm not sure I get what you mean by "streraks" but these are often included with elongate trains of bits of "bakerite". I have had several broken crystals faceted and the cutters have to work a bit to find clean sections. Almost all have very well-developed striations, which may create a streaky optical effect (?) ...see picture.

Impressive size Linus...here's another example of a robust crystal group (small cabinet) from 2009...the crystals are easily 1.3 cm across

Another interesting feature is that although the literature does not indicate good cleavage in nifontovite these crystals show perfect cleavage at an angle to the elongate axis. You can see incipient cleavage planes in crystal on the lower right in the picture.

[Roger Warin]

Thank you, Peter, for these details.
Nifontovite interests me because for me it represents the unusual victory of boron over silicon. It is an anomaly that I can characterize as Dantesque for a mineralogist (even an amateur) admirer of a telluric planet.
I understood the pernicious power of boron when it attacked the granite of the tomb of the Duke of Wellington himself (located in the Crypt of Saint Paul's Cathedral in London-UK). This granite being an igneous rock, underwent a metasomatic process (extreme case of metamorphism with chemical reactions).
This strange, little-documented fact opened a window for me into the frontier of our silicon-based mineral world.
Perhaps one day I will ask Jordi to publish a short note behind the scenes at the FMF forum on my “thoughtful” philosophy of this competition.
The structures of oxygenated boron compounds are mainly trigonal BO3 borate units, but there are also rare tetrahedral BO4 units.
Many natural borates are hydrated.
B-O bonds are short because of the large difference in electronegativity of the elements. The element boron is placed by its properties at the boundaries between metals and non-metals. Boric acid B(OH)3 is an acid and not an amphoteric.
Tourmaline is the mineral with the most abundant boron content with 10% boron.
I am giving these details for all amateurs.

[Peter Megaw]

Great pictures Roger...love those second order colors!

Not sure which tourmaline group member you're calculating those percentages from, but
what about Quingsongite BN which I think runs 44% B by atomic weight?