Barite

From Montana

Life in the USA is not normal. It feels pointless and trivial to be talking about small looks at the fascinating natural world when the country is being dismantled. But these posts will continue, as a statement of resistance. I hope you continue to enjoy and learn from them. Stand Up For Science!

Vincenzo Casciarolo was a simple cobbler in Bologna, Italy, in 1602, when he stumbled upon some interesting rocks on the slopes of Monte Paderno outside town. The remarkably heavy stones had an even more attention-getting property: they glowed in the dark.

Scientific thought in those days tended toward alchemy, despite the futuristic ideas Leonardo da Vinci had expressed a century earlier. And if alchemists pursued anything, they were constantly searching for the Philosopher’s Stone, the substance that would transmute common metal into gold. Casciarolo sought out his local alchemist, one Scipione Begatello, who showed that the rock contained sulfur, another ingredient thought favorable for transformations.

Casciarolo gave up his career as a cobbler to become an amateur alchemist, but aggressive study and analysis showed that Casciarolo’s rock was not the Philosopher’s Stone, but the “Luciferous Stone, which would not itself produce gold, but which would absorb the golden light of the sun, like a new Prometheus stealing a Celestial Treasure,” as Fortunius Licetus (1577-1657) wrote in his book Litheosphorus in 1639-1640.

Casciarolo’s rock was barite, barium sulfate, and the specimens from Monte Paderno probably showed phosphorescence, emitting light after a delay following exposure to sunlight. That’s a property more evident under ultraviolet light and is rare in barite, but it does occur.

My barite specimens here are from Indian Head Rock near Basin, Montana, where barite grows in cracks in brecciated Cretaceous Elkhorn Mountains Volcanics, a thick pile of material erupted around 84 million years ago (for ages, see for example Olson and others, 2016, Geologic map of the Ratio Mountain 7.5′ quadrangle, southwest Montana: Montana Bureau of Mines and Geology EDMAP-10).

View of the cliffs of Elkhorn Mountains Volcanics where barite is found.

At this famous collecting locality, there’s really nothing much in the cavities other than the barite except for occasional crusts of chalcedony. Barium is the 14thmost abundant element in the earth’s crust, more abundant than carbon, chlorine, copper, or lead, and barite, barium sulfate, is the most common barium mineral. Exactly why there is (or was) so much barium at that particular location just west of Basin, Montana, is certainly unclear to me, but barite deposits of diverse forms are not really uncommon worldwide. This deposit was probably a hydrothermal (possibly a hot-spring) setting, and there is some evidence that in marine settings, at least, barite precipitation is enhanced by the presence of certain bacteria (Martinez-Ruiz and others, 2019, Barite formation in the ocean: Origin of amorphous and crystalline precipitates: Chemical Geology, 511:441-451). Whether that might be a factor here, I do not know.

Field of view about 7 cm

Some of these little honey-colored crystals look like cubes, but barite is actually orthorhombic – instead of cubes it makes forms whose three crystallographic axes are perpendicular but are not quite equal in length. So these are not-quite-cubes, and you can see several that are obviously not even close. Barite is famous for its diversity of crystal forms.

Everyone benefits from barite, and not just people who suffer through barium enemas (barium is used for that because it is x-ray opaque). As long as you use gasoline, heat your home with natural gas, or use plastics, you’ve contributed to the barite industry. 90% or more of the barite consumed goes to drilling mud for hydrocarbon exploration, which could not operate without it. The mud helps control pressures in the subsurface to prevent blowouts, and it circulates rock cuttings and other material up to the top of the wells. It’s neither toxic nor hazardous.

Barite is also a component in enamels such as those used in auto paint, and it’s a filler to increase weight and serves as a coater and pigment in lots of things from playing cards and paper to ceramics, plastics, glass, brake pads, and rubber. Its relatively high density makes it useful to provide weight to the “anti-sail” mudflaps on trucks. It’s also an effective x-ray blocker for laboratories and hospitals.

The United States depends on imports for about 87% of its barite needs, imported mostly from India (40%), China (25%), Morocco (17%), and Mexico (14%). Most US production comes from Nevada. Historically, barite deposits near Greenough and Libby, Montana, were mined commercially for a time in the 1950s, and there are numerous occurrences and prospects throughout the state (Berg, 1988, Barite in Montana, MBMG Memoir 61).

Barite (officially, baryte) was named in 1800 by German mineralogist Dietrich Ludwig Gustav Karsten (1768-1810) from Greek βαρύς, varýs, heavy, owing to the mineral’s unusually high specific gravity (4.5, compared to quartz at 2.67).