FMF - Friends of Minerals Forum, discussion and message board

[Roger Warin]

Hello,
Let me introduce you to something other than thin sections, thin tubes!
But I need you, because Chatjpt does not know how to answer my questions: for example, it ignores the existence of the analogous and antilogue poles of tourmaline. However, the answer was discovered a long time ago.
I present to you photos of the hair of the goddess Pele which I believe have never been published. Pele is this Hawaiian goddess of fire, lightning, dance, volcanoes and violence.
The goddess also lost her hair at Pic de la Fournaise (my pics).
I have a request to make to you: what is the composition of these glass fibers?
My photos are taken in binoculars with top circular lighting.
The white stripes are the reflection of a chain of lamps.
To tell the truth, I consider these hairs to be ephemeral tektites.
Am I wrong ?

Some say that the composition is SiO2 (this reminds me of Libyan glass): impossible.
Others: basalt glass = it doesn't say anything.
However, I learned that this phase resulting from volcanic magma must be extremely hot.
This glass cannot have the composition of the initial basalt (I neglect the volatiles) because a physical separation must have occurred to vitrify only part of the magma. Not all volcanoes give Pele's hair, like Hawaii, Pic de la Fournaise, Erta Ale, etc.
I thus compare this to impacts melt also born in drastic conditions.
So next to silica (we are not talking about quartz at these temperatures), there are feldspars.
Some authors have highlighted olivine grains. I don't see anything in XPOL.
But the needles seem very pure. The walnut color comes from the oxidation of iron.

I would like to know your opinion.
THANKS.
Roger.

[carlo11]

Can I suggest you get an oxide analysis of the glass and then just find out what is it made of? That should clear up most questions you might have about pele's hair composition. Also, there might be works that describe and analyze comparable samples on google scholar.

[James Catmur]

You could use the new feature in Mindat:

https://www.mindat.org/ref_search.php?frm_id=cfrm&cform_is_valid=1&refsearch_text=pele%27s+hairs&st=0&submit_cfrm=Search&hid=1&refsearch_type=0&refsearch_yearfrom=&refsearch_yearto=&refsearch_ddc=&refsearch_lcc=&refsearch_pub=&refsearch_auth=&refsearch_dl=0

That seems to give a few references

[Jesse Fisher]

Pele's hair is a common byproduct of active lava fountaining during an eruption of basaltic lava at a volcano such as Hawaii's Kilauea. It is produced during fountaining when escaping volatile gases (mostly H2O and CO2) form bubbles as the lava depressurizes near surface and burst through the surface of the ponded lava. This creates threads from the viscous silicate lava, which cool rapidly when thrown into the air. Accumulations of it in drifts are common down-wind from eruption sites, as seen in the photo (from the Hawaii Volcanoes National Park Facebook page), which was taken during the most recent eruption at Kilauea.

The exact composition of these glass threads is likely to vary a bit, depending on the amount of crystal formation that has happened in the lava/magma prior to eruption. Early forming phenochrysts in the magma will include plagioclase, olivine, and pyroxenes, which will selectively remove Fe, Ca, and Mg from the melt, resulting in an overall concentration of Al and Si. The phenochryst content of of many Hawaiian lavas is fairly low (from my experience looking at them under thin section), so I would suspect that the overall chemistry of the glassy ground-mass would generally reflect the overall basaltic chemistry of the magma.

[marco campos-venuti]

Hi Roger,
A normal explosive volcanic eruption produces glass shards called volcanic ash that will form tuff deposits. Even eruptions dominated by lava flows have a short explosive phase at the beginning. The formation of Pele's hairs instead of glass shards indicates that the magma was very fluid and therefore probably overheated. This phenomenon is rather rare and only possible with basaltic magmas. Rhyolites do not produce hairs. The explosion of gas bubbles produces glass shards because when the bubble stops growing it is just solid and breaks in sharp fragments. On the contrary when the magma is overheated it behaves in a very fluid manner and takes longer to cool, like cotton candy. There is no fractionation between the hair and the rest of the magma, so the composition is the same as the corresponding lava flow.
Pele's hairs are therefore a particular type of volcanic glass. Not an obsidian because this is of rhyolitic composition. In no way therefore can they be considered tektites, as tektites are formed following the impact of a comet which with its water content favors the fusion of terrestrial rocks in the impact site which are expelled and, in some cases even put into orbit. Some of these fall to the ground with the characteristic ablation surface. There is no ablation in any product of volcanic eruptions.

[James Catmur]

I have only ever found lava rope (Popocatepetl), lava bombs (Hill of Tarvit) and obsidian (Michoacan) but never Pele's hair