The dates

Sentences without a label are documented facts; the others are marked "probable" or "uncertain".

The essential dates of the portal, from the birth of the rock, about 30 million years ago, to the exploration permit of 2026. Each row has its source, with the page. A date is the one the source maintains: for the oldest centuries it is often a hypothesis. The dates on which the sources do not agree are gathered at the end.

The rock and the origins

When	What	Source
about 30 million years ago	The magma comes to a stop beneath the valley and becomes the Traversella pluton, while the uplift of the Alps is slowing down	Costa et al. 2019, p. 6; Munari 2019, p. 39
AD 367-375	Coin of Gratian, one of the four found at the Balma Bianca	Barello 2022, slides 4-5
AD 388-395	Coin of Theodosius I, from the mint of Siscia, from the same hoard	Barello 2022, slides 4-5
end of the 5th century or soon after	A fourth coin, very light, seems to imitate a monogram of Zeno and would move the hoard to this date uncertain	Barello, Rubat Borel 2019, pp. 177-178
between the end of the empire and the age of the Goths	According to Barello and Rubat Borel someone lived in the Balma Bianca cavity, perhaps briefly; the coins do not prove a Roman mine	Barello, Rubat Borel 2019, p. 178
Roman times	According to Chiappino silver-bearing galena is dug at Brosso uncertain	Chiappino 2010, p. 24
early 11th century	According to Chiappino the first reliable documents on Brosso uncertain	Chiappino 2010, p. 24

From the 14th to the 17th century

When	What	Source
14th and 15th centuries	The lords of the Val di Brosso also control the mineral resources and the furnaces	Gravela 2021, p. 41
1386	The tuchinaggio, the Tuchini revolt, begins in the Val di Brosso; according to Costa the revolt perhaps also arises from the tax on the ore probable	Gravela 2021, p. 41; Costa, Garabello 2022, slide 12
1391	Amadeus VII gives the valleys back to the local lords	Gravela 2021, p. 44
1446-1451	Second revolt, put down in 1451 according to Gravela; for Chiappino the revolts last "almost a century" uncertain	Gravela 2021, pp. 32, 44; Chiappino 2010, p. 24
1448	According to Costa the count of San Martino regains control	Costa, Garabello 2022, slide 12
1487	A ruling of the Savoy administration leaves the inhabitants of Brosso and Traversella in free possession of the iron ore: it is the oldest documented record of the diggings	Costa et al. 2019, p. 9; Jervis 1873, p. 121
1 January 1497	More than ninety heads of family of Brosso give themselves the statutes for work in the mines	Bertolotti 1871, pp. 29-32
29 March 1504	Duke Philibert of Savoy confirms the statutes	Bertolotti 1871, p. 43
1561	According to Chiappino, Emmanuel Philibert recognises that the owner of the land also owns the subsoil and the minerals probable	Chiappino 2010, p. 25
1570	In a lawsuit we read that at Traversella ore has been dug "for 10, 20, 30, 40, 50, 60 and more years"	Costa et al. 2019, p. 9
5 November 1575	The Chamber of Accounts in Turin rules in favour of the people of Brosso against the duke's procurator of the patrimony probable	Chiappino 1996, p. 45
1604-1672	A municipal register of Brosso records the ore dug from each croso, one of the small mine workings	Bertolotti 1871, p. 24

The 18th century

When	What	Source
1715	Pyrite appears in the annals of Brosso and the green vitriol factory is founded at Bore probable	Brosso ecomuseum page, «Cronologia delle miniere»
1716	Bernardo Mutta finds the main vein at the Pian del Gallo; the mines grow "probably" thanks to this discovery probable	Costa et al. 2019, p. 9
1720	Giuseppe Triverio founds the Meugliano blast furnace, perhaps the first in the area	Berattino 1988, pp. 297-299
1723	The House of Savoy taxes the ore by weight	Costa et al. 2019, p. 9
1732	The golden age of Traversella begins, which for Costa lasts until 1884 probable	Costa et al. 2019, p. 10
1745	100,000 rubbi of ore, about 920 tonnes probable	Costa et al. 2019, p. 11
1750	190,000 rubbi probable; Antonio Gattino, iron master, buys the crosi of Bernardo Paglia	Costa et al. 2019, p. 11; Berattino 1988, pp. 297-300
1769	Count Valperga and Francesco Chiumino found a company that gives a boost to the vitriol factories probable	Chiappino 2010, p. 26
1774	The Ubertino forge, according to the trail's information pages; no document confirms it uncertain	inalto.org, online page
16 or 26 June 1781	King Victor Amadeus III grants Francesco Chiumino the vitriol privilege for fifteen years uncertain	Chiappino 1996, p. 46; Brosso ecomuseum page
1794	700,000 rubbi of ore	Costa et al. 2019, p. 11
1794-1799	The lawyer Gian Martino Biava "Caloni" smelts the ore in the Prelle area, on the left bank of the Chiusella	Berattino 1988, pp. 278, 285

The 19th century

When	What	Source
29 June - 2 July 1819	The Riondello landslide: the total collapse comes on 2 July, a feast day, with no victims	Berattino 1988, p. 140
1819-1822	The ore dug rises from 282,100 to 735,188 rubbi, by digging in the collapsed mass and even in the pillars	Berattino 1988, p. 141
1829	The peak: almost a million rubbi; for Berattino 954,550, in a part of the page that is hard to read uncertain	Costa et al. 2019, p. 11; Berattino 1988, p. 176
1829	Falquet and Banchieri write that children of ten to twelve carry the ore to the surface	Berattino 1988, p. 170
13 July 1829	The town council writes that almost all the families live on the diggings, "even the boys"	Berattino 1988, pp. 176-177
1832	The "Gastaldetti" carriage road from Traversella to Strambinello is ready	Berattino 1988, pp. 260-263
22 February 1839	The first of the three deeds with which the Sclopis brothers buy the Brosso mines probable	Chiappino 1996, p. 47
1849	According to Jervis the Traversella blast furnace goes out and the iron mines close	Jervis 1873, pp. 122, 124
end of 1854	Quintino Sella tries out the first machine: a wooden disc with a single electromagnet	Burci 1860, pp. 8-10
19 July 1855	Sella obtains the privativa, the forerunner of the patent, and commissions from Froment the machine with 48 electromagnets	Burci 1860, pp. 10-11
1855	The pyrite of Brosso goes to the Sclopis sulphuric acid factory in Turin probable	Brosso ecomuseum page, «Cronologia delle miniere»
1858	Froment's machine is exhibited in Turin; the Sclopis factory no longer depends on foreign supplies probable	Burci 1860, pp. 10-11; Chiappino 2010, p. 26
1859	Count Riccardi di Netro receives the Castiglione concession; according to Chiappino a law declares the subsoil the property of the Nation probable	Jervis 1873, p. 124; Chiappino 2010, p. 25
1862	Zampari counts 2,200 tonnes of pyrite a year at Brosso	Zampari 1862, pp. 1-2
1872	The Bore vitriol factory is closed and demolished probable	Chiappino 2010, p. 26
1883	The last owner declares 17,000 rubbi; the magnetite produced amounts to 161 tonnes	Costa et al. 2019, p. 10; Berattino 1988, p. 317
1884	According to Costa the Traversella mines close	Costa et al. 2019, p. 10

The 20th century

When	What	Source
1900	The Traversella mines pass to the Società Anonima delle Miniere di Traversella	Costa et al. 2019, p. 10
1902	Froment achieves separation by flotation	Costa, Garabello 2022, slides 25-26
1904	The flotation patent is sold for 225 pounds to Minerals Separation Ltd	Costa et al. 2019, p. 12
1907	At Brosso a 3,500-metre cableway carries the pyrite from Valcava to the station of Montalto Dora probable	Chiappino 2010, p. 26
first week of July and 20 September 1907	The pay book shows that most of the Brosso workers do not turn up for work	Vescovo 2002, p. 66
February 1908	The "Lega dei Minatori della Valle di Brosso", the Miners' League of the Brosso valley, is born	Vescovo 2002, pp. 68-69
21 February 1909	The League unveils its red flag at Brosso	Vescovo 2002, pp. 74-75
October 1911	Last record of the League, in a letter from the mine director	Vescovo 2002, p. 78
1913-1914	The Traversella mines pass to the Società Ferriere Piemontesi and then to FIAT	Berattino 1988, p. 197
1931	At Brosso the mines pass to Montecatini, the Italian mining and chemical company probable	Vescovo 2002, pp. 79-80
1938 or 1939	A cableway carries the Traversella ore to the station of Montalto Dora: 1938 for Costa, 1939 for Berattino uncertain	Costa et al. 2019, p. 10; Berattino 1988, p. 263
around 1940	FIAT builds the crushing silo probable	Museo della Miniera website, «Il Museo»
the 1950s	The Bracco Giorgio D tunnel, with a 114-metre shaft and two lifts probable	Museo della Miniera website, «Piazzale Bracco Giorgio D»
1964 or soon after	The Brosso mine closes: 1964 for Chiappino and the ecomuseum, "the 60s" for Vescovo uncertain	Chiappino 1996, pp. 49, 55; Vescovo 2002, p. 80
1965	Traversella still yields 100 tonnes of ore a day	Baldassarre et al. 2025, p. 3
1969	According to Beratto extraction ceases	Beratto (thesis), p. 30
September 1971	The Traversella mine closes; the month comes from the ecomuseum probable	Costa et al. 2019, p. 10; Traversella ecomuseum page, «Visita al museo»

After the closure

When	What	Source
after 1971	The village miners are guaranteed work in the FIAT plants in Turin	Berattino 1988, p. 236
22 September 1981	A flood destroys most of the mine buildings	Berattino 1988, p. 236
1998	The ecomuseum "Il Ferro e la Diorite", Iron and Diorite, is born from the restoration of the mine buildings probable	Provincia di Torino page, «Ecomuseo Il Ferro e la Diorite»
2005 or 2007	The museum opens: created in 2007 for Costa, already open to the public in 2005 for CRESTA uncertain	Costa et al. 2019, p. 17; CRESTA, online page
2010	The Gruppo Mineralogico Valchiusella, the mineral club of the Chiusella valley, finds the Balma Bianca coins	Barello, Rubat Borel 2019, p. 176
August 2013	The coins go on display in the Traversella museum	Barello, Rubat Borel 2019, p. 176
20 September 2025	The renewed, accessible museum is opened probable	Giornale La Voce, 20 September 2025
13 January 2026	The Region grants Raw Materials Italia a two-year exploration permit over 94.8 hectares	regional decision of 13 January 2026 no. 6, p. 5
2 February 2026	The "Complesso estrattivo del Plutone di Traversella", the mining complex of the Traversella pluton, enters the Region's Register of geosites, as of national interest	regional decision of 2 February 2026 no. 148, p. 5

The disputed dates

On these dates the sources do not agree; the page "Who thinks otherwise" tells them in full.

The vitriol privilege: 16 June 1781 for Chiappino, 26 June for the ecomuseum uncertain.
The Traversella cableway: 1938 for Costa, 1939 for Berattino uncertain.
The closure of Brosso: 1964, 1964-66 or "the 60s" uncertain.
The end of iron at Traversella: 1849 for Jervis, 1883-1884 for Costa.
The Riondello landslide: 29 June 1819 for Beratto, total collapse on 2 July for Despines; Torti dates it to 1816, probably by mistake uncertain.
FIAT: owner from 1914 for Costa, from 1913 for the museum's website uncertain.
The tax of 5 denari per rubbo: in 1723 or in 1753 uncertain.
The edict on the distances between shafts: 1787 for Torti and Costa, 9 December 1797 for Beratto uncertain.
The flotation patent: sold for 225 pounds according to Costa, for 25 according to Torti probable.
The museum: created in 2007 or already open in 2005 uncertain.

Sources: Chiappino 1996, p. 46; Costa et al. 2019, pp. 9-10, 12; Berattino 1988, pp. 140, 263; Jervis 1873, p. 122; Beratto (thesis), pp. 26-27; Torti 1973, pp. 4, 8; Vescovo 2002, p. 80; Museo della Miniera website, «Il comprensorio minerario»; CRESTA, online page

Sources for this page

E. Costa, G.A. Dino, P. Benna, P. Rossetti, The Traversella Mining Site as Piemonte Geosite, in «Geoheritage», 11(1), 2019, pp. 55-70 (page numbers are those of the post-print, 1-24).
E. Costa, D. Garabello, La produzione di magnetite a Traversella (Lo sfruttamento delle miniere durante il XVIII e XIX secolo), presentation at the AIPSAM round table, Traversella, 1 October 2022 (slides are cited).
P. Munari, Valchiusella: le rocce raccontano. L'impronta geologica su paesaggio, cultura e attività umane, Press Up, 2019. (popular work)
F. Barello, La frequentazione della miniera di Balma Bianca attraverso un importante rinvenimento numismatico tardoantico, presentation at the AIPSAM round table, Traversella, 1 October 2022.
F. Barello, F. Rubat Borel, Traversella, località Balma Bianca. Rinvenimento di monete tardoantiche all'ingresso di una miniera, in «Quaderni di archeologia del Piemonte», 3, 2019, pp. 176-178.
C. Chiappino, Le miniere di Brosso: un patrimonio millenario di storia umana e scientifica, in «Opera Ipogea», 1/2010, pp. 23-30.
C. Chiappino, Recupero e valorizzazione a scopo museale della Miniera di Brosso, degree thesis in Engineering, Politecnico di Torino, 1996.
M. Gravela, Prima dei Tuchini. Fedeltà di parte e comunità nelle valli del Canavese (Piemonte, secolo XIV), in A. Fiore, L. Provero (eds), La signoria rurale nell'Italia del tardo medioevo, 3. L'azione politica locale, Florence, Firenze University Press, 2021, pp. 31-49.
G. Jervis, I tesori sotterranei dell'Italia, vol. 1 (Alpi), Turin, Loescher, 1873.
A. Bertolotti, Statuti minerari della Valle di Brosso del secolo XV, Turin, Stamperia Reale, 1871.
G. Berattino, Le miniere dei «Baduj» di Traversella, Ivrea, Ferraro, 1988.
G. Burci, L'elettricità applicata alla preparazione meccanica del minerale di rame estratto dalla miniera di Traversella in Piemonte, Pisa, Tipografia Pieraccini, 1860.
F. Zampari, Relazione sulla miniera di pirite di ferro di Brozzo dei Fratelli Sclopis, Turin, 28 December 1862 (unnumbered pages, counted 1-3).
M. Vescovo, Situazione storico-economica della Valle di Brosso dal XV al XX secolo, final dissertation, Faculty of Political Science, University of Turin, academic year 2001/2002.
R. Beratto, Studio geologico dei corpi minerari del giacimento di Traversella, degree thesis in Geological Sciences, University of Turin (year not given; survey in the tunnels 2001-2002).
R. Torti, La miniera di Traversella e i suoi minerali, Quaderno GML no. 10, Milan, Gruppo Mineralogico Lombardo, 1973.
G. Baldassarre et al., Exploring the Recovery Potential of Critical and Strategic Raw Materials from Traversella Mine (Piedmont, Italy) Waste: A Comparison of Laboratory-Scale Separation Techniques, in «Mining», 5(2): 21, 2025.
Regione Piemonte, D.D. 13 January 2026 no. 6, mining exploration permit «Traversella» P0065T, in «Bollettino ufficiale» no. 3 of 22 January 2026.
Regione Piemonte, D.D. 2 February 2026 no. 148, update of the Region's Register of geosites, in «Bollettino ufficiale» no. 6 of 12 February 2026.
Museo della Miniera di Traversella, official website, https://mmttraversella.it/, consulted on 16 October 2026.
Provincia di Torino, Ecomuseo, Museo mineralogico di Brosso and Centro minerario di cultura di Traversella, online pages (website closed; Internet Archive copies), consulted on 16 October 2026; pages Ecomuseo «Il Ferro e la Diorite», consulted on 16 October 2026.
CRESTA, University of Turin, Traversella, il ferro raccontato dalla montagna, online page, consulted on 15 October 2026. (popular work)
Giornale La Voce, Traversella inaugura il Museo delle Miniere accessibile, 20 September 2025. (popular work)
inalto.org, Sentiero delle Vote da Calea, online page, consulted on 15 October 2026. (popular work)