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  LL5

TKW 3.7 kg. Observed fall 1794 in Toscana, Italy.

     

Steve writes:

As far as sciences go, meteoritics is considered a relative newcomer. France’s 1803 L'Aigle fall is commonly cited as the defining event that heralded in this new discipline, with principal credit for the acceptance of rocks falling from space often given to a widely published report by French physicist, astronomer, and mathematician Jean-Baptiste Biot – a report said to be significant because it presented both physical (the actual stones) and moral (eyewitness) evidence that made a terrestrial origin for L’Aigle unlikely. But while Biot’s report may have been considered especially pivotal because of its commission by the French Academy of Sciences, it occurred almost a decade after the Siena fall, which in reality was studied by more scholars who provided the same kinds of compelling evidence as did Biot. As a consequence of that and other considerations described below, many believe Siena to be the far more influential fall.

On June 16, 1794 at approximately 7:00 pm, eyewitnesses described a high dark cloud that emitted smoke, sparks that looked like those from the tails of rockets, and bolts of unusually slow-moving red lightning. A tremendous explosion subsequently showered an area southeast of Siena, Italy with stones ranging in size from a few milligrams to one weighing almost 3 kilos, in all having a total known weight exceeding 3.7 kg.

Siena – an LL5 chondrite – was the first fall to occur within the vicinity of a sizeable European city. As a result, scholars from several Italian universities came to the area to study the event – a task complicated by Mount Vesuvius’ eruption only 18 hours earlier. In fact, many argued the stones were either ejecta from the volcano (about 200 miles southeast of Siena) or a heated consolidation of the volcano’s expelled dust and ash.

Despite the timing of the eruption and the academics of the Enlightenment having decisively ruled out the possibility of anything actually falling from the heavens, traditional explanations for Siena’s source were contradicted by countless eyewitness accounts and the many stones recovered from the fall. To the university scholars who studied the Siena event, the only realistic origin was an extra-terrestrial one. As a result, their work and unorthodox conclusion opened up a new dialog on this subject long before L’Aigle’s eventual fall nine years later.

Siena fell only two months after the publication of German physicist and musician Ernst F. F. Chladni's book "On the Origin of Iron masses". His studies of historical records convinced Chladni of an extra-terrestrial source for stone and iron fragments reported as having fallen from sky. But because news traveled slowly in the 18th century, it wasn’t until two years later that the first report of the Siena fall appeared in a 1796 Berlin paper. Without the benefit of the Siena investigator’s conclusions, Chladni’s book received mostly negative reviews in Germany throughout 1794 and 1795. But while it took the same two years for his book to reach England, travelers had already returned from Italy with both stories about Siena and actual pieces of the meteorite (including bogus examples fabricated by unscrupulous locals for unsuspecting tourists), which contributed to Chladni’s book being more favorably received by the English academia.

There were other reasons for England’s increasing willingness to believe that rocks could fall from space. Sir William Hamilton was the English Ambassador at Naples, and the Royal Society’s 1795 publication of his account of Mount Vesuvius’ eruption included a short discussion about the Siena stones. Then on December 13th of that same year, a 25 kg chondrite fell at Wold Cottage in Yorkshire, adding additional support for the theory of meteorites’ extra-terrestrial origins. Shortly thereafter, Edward King – a Fellow of the Royal Society – in early 1796 published the first English book about fallen stones. He focused primarily on the Siena event, but just as he was finishing it, he received a copy of Chladni's work. To bolster his conclusions, King revised his manuscript to quote extensively from Chladni. King's 36-page book was widely read, and while it was still received with some controversy, it influenced the growing ranks who believed meteorites actually originated off Earth. In fact, as a consequence of reading King’s book, one of five witnesses to a meteorite that fell 17 years earlier in Pettiswood, County Westmeath, Ireland – a meteorite that hadn’t been previously reported by any of the witnesses for fear of ridicule – finally felt comfortable enough to come forward (the account was subsequently published in a 1796 issue of The Gentleman’s Magazine and described the meteorite as having landed on a wooden part of a horse carriage that broke into three pieces and caused the horse to fall to the ground; unfortunately, while two farm laborers were said to have collected fragments from the meteorite, none is currently known to exist today).

As an interesting aside, one of the more decisive reports on Siena came from James Smithson, an English scientist that never visited the U.S., but who bequeathed his estate to found the Smithsonian Institution in Washington for "the increase and diffusion of knowledge". Smithson, who happened to be in Florence at the time and heard of the meteorite shortly after its fall, immediately traveled to Siena. Like the Italian researchers, Smithson also extensively interviewed local residents. His efforts (including reporting eyewitness accounts to Henry Cavendish, the British scientist who discovered hydrogen) helped contribute to the growing body of evidence that pointed to the extra-terrestrial origin of meteorites; as a result, subsequent reported falls were being treated in Europe with less skepticism – except in France, where a number of highly regarded academics remained unconvinced until Biot’s subsequent report on L’Aigle almost a decade later.

So while L’Aigle is often credited as having convinced "enlightened" scholars that rocks can indeed fall from the sky, one can comfortably argue it was Siena that paved the way for the new science of meteoritics by having started nine years earlier the reevaluation of deep-rooted beliefs about the origin of fallen stones and irons.

For a short time, I decided it would be fun to collect small examples of historic meteorites and display them as a set. While more contemporary ones like Murchison or Allende provided tremendous scientific knowledge, I arbitrarily decided the focus of my collection would be on those that changed mankind’s fundamental views about meteorites and their origins. Consequently, several of the meteorites described in this post appear in my "historics" display case shown in Photo 1 (Siena is more easily seen in Photos 2 and 3, the former in a 5.5" by 4.5" Riker mount).

In a related vein, several years ago I was fortunate to be able to acquire one of only a handful of Karl Franz Anton Ritter von Schreibers’ Beytrage zur Geschichte und Kenntniss Meteorischer Stein- und Metall-Massen (Contributions to the History and Knowledge of Meteoric Stones and Irons) – a book about meteorites he self-published in 1820. The eventual namesake for the mineral Schreibersite, von Schreibers was an Austrian naturalist trained as a physician. He was also a competent zoologist and botanist, with an additional passion for minerals – especially meteorites. The Vienna Natural History Museum appointed von Schreibers to its director’s position in 1806, where despite a fire in 1848, his original collection of meteorites can still be seen today. von Schreibers’ book was significant for several reasons: it was the first to describe a particular meteorite collection; it was likely the first geology book anywhere to be illustrated with lithographs (lithography was only invented around 1800); and it included the first formal description of using heat or acid to expose Widmanstätten patterns (including a "nature print" individually inked and stamped from Widmanstätten’s actual slice of Elbogen on which he made his original observations). That book also described von Schreibers’ Siena individual. He noted its crust (which he referred to as "rind" or "bark") as being "particularly tender and thin", almost coal-black but somewhat gray in color, with a "silky white shimmering sheen" and no external appearance of its metal content. While I can’t read German, for those that can, the relevant pages are shown in Photo 4 (the lower right illustration on the photo page shows von Schriebers’ personal Siena stone).

Around the same time that I acquired von Schreibers’ book, I was also able to obtain thin sections of L’Aigle and Siena (the former was previously featured in my 8/18/2020 MPOD post). Photos 5 and 6 show the Siena thin section in xpol and white light, respectively. Photo’s 7 through 11 blow up a few interesting areas (Photos 9 and 10 are paired, showing approximately the same area separately under both kinds of light). You can also zoom and pan around the entire thin section images on GigaPan:

Between Crossed Polarizers

White Light

[For those new to GigaPan, click on the diagonal arrows to the right of the image to enter full screen mode, then use your mouse and its scroll wheel to pan around and zoom in and out.]