3:45 pm, clear sky
A brilliant fireball crosses above Cluj, from the north-west to the south-east, trailing a broad band of smoke. At the head of the band, some see a ball of fire. The band hangs in the sky for minutes.
Mociu, Cluj county · 3 February 1882
One Friday in February, it rained stones over Mociu
Yes, it really happened: on a clear afternoon, a fireball broke into thousands of pieces above a few villages in Cluj, and the stones came down on snow. A professor weighed them soon after. Its number got mangled on the way, in an American paper, and this page shows the true reckoning.
The fall
Minute by minute
From fireball to silence, in a single afternoon.
Stones down
3,000 stones
Three detonations
About three minutes later, deep, long detonations roll in from the north-east and rattle windows. At Coasta (then Gyulatelke), a boy counts three loud bangs, then rattling like gunfire and humming like wind. That is the sound of falling stones.
Stones on snow
The stones strike the forest branches and land on thin snow. At Vișea, one the size of a pigeon's egg drops among the people gathered in the street. Another lands on a widow's house, and she picks it up still markedly warm.
Silence, then the professor
After the fall, nothing is left in the sky but a small dark cloudlet. Two days later, geology professor Antal Koch arrives with his colleague, sent by the Transylvanian Museum, and starts buying stones from the villagers. By summer the count reaches 911 stones and 174 kilograms.
First bet
Which end got the big stones?
The fireball first appeared in the north-west and died out above Mociu, in the south-east. Did the heavy stones fly furthest, or drop first? Pick an end, and the map below will show the answer.
The end with the big stones is…
In the south-east. Small stones fell thickly at the north-western end, and the few heavy ones at the other end, around Ghirișu Român and Mociu. Koch drew the rule on his map through the size of the dots.
His explanation is simple: the small pieces were the first to lose the speed they had brought from space, while the big ones kept it longest, so they fell separately, further on. The same had happened at Pultusk in 1868.
The map below begins with this question.
The map
The stone field, from Coasta to Mociu
Each dot is a village. Touch it to see which stones were found there. Big dots mean big stones, as on Koch's map.
Nine villages, one afternoon
The field stretches about 14 kilometres, from Coasta to Mociu. Koch measured it as 15 by 3 kilometres, about 45 square kilometres; drawn around the villages that yielded stones, the outline here comes out at 66.
North-west: dense rain, small stones
Around Coasta, Vișea and Bărăi the stones fell thickly but small. Koch did not find a single one himself, though he looked: his guides spotted them better, on the snow.
Middle: bigger stones, rarer
Around Vaida-Cămăraș and Pălatca the pieces grow bigger and rarer. In the Pălatca forest a stone of more than 8 kilograms was found, which its finder split with an axe out of curiosity.
South-east: few, but huge
At Chesău, Ghirișu Român and Mociu the biggest stones fell, including the biggest piece, from the edge of the Paphely wood. The sample the Cluj researchers studied is from Chesău too.
What is missing from the map
At Bogács, 4 kilometres east of Coasta, people told of fallen stones, but Koch doubted them: the direction did not fit the fireball's path. On this map, the dot is missing.
The outline is redrawn from Koch's 1882 map, fitted to the villages' present positions; its area is computed by the program, not measured by Koch. The dots sit on the villages' present coordinates.
Second bet
How heavy was the biggest stone?
Koch weighed it in Cluj, soon after the fall. Since then its number has travelled through books and catalogues, and picked up an error on the way. Pick a weight, then see the reckoning.
The biggest stone weighed…
35.70 kilograms. That is what Koch's scales showed for the piece that came down at the edge of the Paphely wood, after breaking an oak's branches and driving 65 centimetres into the frozen ground.
And 56 kilograms? That is what an American paper printed in 1961, misreading Koch's account. Koch's 56 kilograms were the museum's whole drawer: 102 stones together. The error is 65 years old today.
Every stone weighed by name is in the next chapter, beside your hand.
Hands on
How big is a stone from the sky?
Pick a stone from the 13 weighed by name and set your hand beside it, at true scale. Each size is computed as a sphere of the same rock.
A sphere of the same rock would be 27.6 cm across: you cannot cup it in one hand.
- Weight
- 35.70 kg
- Fell at
- Mociu, edge of the Paphely wood
- Today
- Cluj, the university
- Size
- 27.6 cm
Sizes are sphere diameters at 3.25 g/cm³, computed from Koch's weighings. True stones have corners, but the size stays nearly the same.
The biggest needs both arms; the smallest of them, under 70 grams, sits in a child's fist.
Outside, all of them wear the burnt crust of the fall. For the inside, see the next chapter.
The 13 stones, biggest first
35.70 kg · the giant of the fall
Mociu, edge of the Paphely wood · Cluj, the university. 27.6 cm.
8.37 kg · the second largest
Ghirișu Român · Budapest, the national museum. 17.0 cm.
8.15 kg · the stone split with an axe
the Pălatca forest · private collection. 16.9 cm.
6.06 kg · the merchant's stone
Ghirișu Român · private collection. 15.3 cm.
5.60 kg · the Vienna stone
Ghirișu Român · Vienna, the imperial museum. 14.9 cm.
4.75 kg · the untouched piece
Chesău · Zsobok, the Mike collection. 14.1 cm.
4.60 kg · the London cube
Chesău · London, the British Museum. 13.9 cm.
3.50 kg · the London pyramid
between Ghirișu and Mociu · London, the British Museum. 12.7 cm.
3.19 kg · the Aiud college stone
Vaida-Cămăraș · Aiud, Bethlen College. 12.3 cm.
3.18 kg · Mociu's second stone
Mociu · Cluj, the university. 12.3 cm.
2.15 kg · the Cluj college stone
Vaida-Cămăraș · Cluj, the Reformed College. 10.8 cm.
2.13 kg · the boundary stone
the Pălatca–Chesău boundary · Cluj, the Azbey collection. 10.8 cm.
69.9 g · the photographed stone
not specified · photographed from a collection. 3.5 cm.
The rock
Black outside, grey inside
Break a Mociu stone and see why people always knew it was no local rock.
Outside, intact pieces wear a fusion crust under a millimetre thick, smooth and glassy like varnish, dark reddish-brown. That burnt crust is the mark of falling through air: the stone's surface melted, and the air blew the melt away.
Inside, the rock is light ash-grey, with brown and black veinlets and sparse metal grains that glint. It is crumbly: small ones can be rubbed between the fingers. In damp air it rusts fast around the iron grains.
Specialists call it an L5-6 chondrite, from the family that most stones from the sky belong to: about nine in ten.
Traces
Where the stones are today
Of the roughly 300 kilograms that fell, pieces sit in more than 30 museums worldwide. The most important are here.
Vienna
The largest collection of Mociu stones sits in the Natural History Museum, in the meteorite hall.
Cluj
The 35.70 kilogram giant stayed with the university, along with dozens of other stones; the samples studied in Cluj were cut from them.
London
The Natural History Museum keeps the 3.5 kg pyramid and the 4.6 kg cube.
Budapest
The 8.370 kg stone reached the Hungarian National Museum through the Transylvanian museum.
Bucharest, Aiud, Dej
Another 11 pieces: 3 at Bucharest university, 7 at the Aiud museum and one at the Dej school.
The rest of the 911 stones gathered by the summer of 1882 scattered through small collections and private hands. Koch himself wrote that the stones are found, smashed and carried off.
The museum counts come from the 1968–1979 catalogues; nobody has counted them all since.
The game
Eight statements, true or false
How much of the stone rain did you keep? Pick, then see the answer with its source.
1 of 8
Why.
Source: …
You have barely lifted the first stone Snowfield gleaner You hold Koch's scales
Method
What we know and what we do not
The weights and places come from Koch's February 1882 report, read in the German original. The summer accounts, 911 stones, 174.115 kilograms, about 3,000 stones and about 300 kilograms fallen, come from his supplementary report, known here only through quotation in the 1980 centenary article. Where the sources disagree, the page sets them face to face.
Stone sizes are sphere diameters at 3.25 g/cm³: Koch's powder weighing (3.609), thinned by one-tenth for pores, following the 5–15% range in the literature. The map is redrawn from Koch's map, and the drawn outline's area is computed by the program, not by Koch.
What the sources do not say
- No source read gives the fireball's mass, speed or orbit before it entered the atmosphere: only its path across the sky, the time and the noise.
- The pages of Koch's supplementary report were not read directly, and the meteorite's electronic record could not be opened by the program. The summer figures come via quotation and are marked as such.
- Koch writes 45 square kilometres; the 1980 article credits him with 60. The outline on this map comes out at 66.
- Few stones have their weight by name in the sources: 13 fit in the chapter above. Koch's dots are size classes. No catalogue lists every stone.
- There is no complete table of the falls from today's Romania, so the page ranks no falls against each other.
- The museum counts are 1968–1979 catalogue states; nobody has counted them all since.
The fall
- Koch, A. (1882). Meteorsteinfall von Möcs in Siebenbürgen. Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften, Mathematisch-Naturwissenschaftliche Classe 85, pp. 116–129. archive.org the February report: time, fireball path, witnesses, the 102 stones, the map
- Tschermak, G. (1882). Über die Meteoriten von Mocs. Ibid. 85, pp. 195–209. archive.org 3:45 pm, the shapes of the stones, the stones that reached Vienna
- Mason, B., Wiik, H.B. (1961). The composition of the Ottawa, Chateau-Renard, Mocs, and New Concord meteorites. American Museum Novitates 2069. archive.org the source of the “56 kg stone” error
- Brassói Fuchs, H. (1980). Száz éves a mócsi meteorit. Földtani Tudománytörténeti Évkönyv 9, pp. 263–272. epa.oszk.hu the summer accounts, the 911 stones, the museums (in Hungarian, with an English summary)
The rock
- Tănăselia, C. et al. (2010). Preliminary investigation of Mocs meteorite by lead isotopic ratio. Studia UBB Chemia LV(3). PDF the L5-6 type, the 3,000 stones, sample I.34B from Chesău
- Tănăselia, C. et al. (2016). Revised rare earth elements composition of Mocs meteorite. Studia UBB Chemia LXI(3). PDF the naming rule, the 9 falls from Romania's territory
- Korotev, R.L. Meteorite fusion crust. Some Meteorite Information, Washington University in St. Louis. wustl.edu what a fusion crust is
- Flynn, G.J. et al. (2023). Physical properties of the stone meteorites (invited review). NASA NTRS 20230000872. PDF chondrite density and porosity
The places and museums
- Naturhistorisches Museum Wien (2012). Presseinformation zur Neueröffnung des Meteoritensaals. nhm.at the largest Mociu collection sits in Vienna
- The fall-field villages' articles on Romanian and Hungarian Wikipedia. wikipedia.org old and new names, coordinates