Could someone tell - it has a density of 2.9, more or less - if this rock is of volcanic or maybe of extraterrestrial (meteorite) nature? I found it a few days ago on a beach, in Northern Portugal, thousands of km away from any active volcano.
First of all try to get a 3D micro-CT image of the object, then try to determine the major elements by XRF. Then, if you have access to a LA-ICM-MS instrument, try to determine the REE distribution with respect to chondrite.
By gamma ray spectrometry, you could determine the content of natural radioactive elements. May be, in a ulta-low background laboratory, you could try to evidence the Al-26 cosmogenic isotope.
I agree with Andrew Beck, It seems a terrestrial basalt. Do not worry if in North Portugal there is no sign of an active volcanoe, it may belong to an ancient basaltic lava flow.
Judging from the available photos, it is not a meteorite. Although vesicle meteorites are known, they are very rare and vesicles are of much smaller size.
I would agree with others - it looks like terrestrial basaltic rock
I should have noticed the vesicles. Thank you for calling my attention to this important detail.
And, above all, many thanks to everyone for responding so quickly and for having dedicated your time to this issue.
Due to the lack of volcanic rocks in the surroundings and the spot of find on a beach, I would suggest your find is probably an artificial clincker or slag, which where commonly used as ship ballast since centuries (rather than a natural product like a basalt)
For your question there is a less complicated flowchart often used by meteorite specialists:
"did I have found a meteorite?" ---> "No"
(Thats sounds like a (not very good) joke, but it is statistical proved as long as you are moving outside the well known strewnfields. ;) )
Best regards
Johannes
Most definitely not a meteorite. If it were then either it would have some degree of magnetic affinity or if one opened it, or preferably cut it open, close examination would show a distinct border between the burnt outer layer and the inside in the case of a stony meteorite. The mineralisation would also be distinct. While volcanoes may not be around, volcanic rocks do travel. But I would suggest that iron production would be around during relatively recent history. This piece looks very much like a piece of slag. The comment about clinker is very apt as all nature of cheap stony material was needed as ballast in the days of tall ships, but in this case it was normally empty ships that went to the Americas from Europe that would be loaded down with material that would be dumped to take on goods to be brought back to Europe. This is how many cobblestones got to North America and why one can find flint from France on the northern shore of Prince Edward Island where Jacques Cartier dumped it. My bet is on ordinary waterworn slag washed up on shore.
Agree with the above. It does look very like slag I have worked on... but could well be volcanic. The very large vesicles and apparent absence of a fusion crust make it very unlikely that this is a meteorite.... a thin section would solve the mystery.and make sure it is not an rare achondritic sample.
I think it's a volcanic rock, certainly basaltic rock in agreed with the density.
The density of meteorites are > 3 or 3.5 but not less
@ Gwènolé: not touching the determination the pebble shown here is an artificial slag or a natural vesicular basalt (and definitly no meteorite), but your statement about meteorite densities is not completely correct. "Tagish Lake" has (for example) a density between 1,5 -1,48 g/cm³, and there are several other examples not reaching the 3 g/cm³ you mention, belonging to CM, CI, CO and CV-group; also H, L and LL chondrites with higher porosities, and a lot of achondrites (eucrites, lunars and others)
Best regards
Johannes
Dear Johannes, Jeffrey and David
I have retained two major issues from your truly interesting answers.
The first was the slag hypothesis. Indeed, looking at some slag images, I found their very similar with “my meteorite”. Nevertheless, I have approched a magnet and nothing happened… Still, it could be slag from a non-ferrous metal, of course.
The other issue was the migration of rocks through the ships travelling the Atlantic Ocean. Indeed, the beach where I found the rock is also full of flint – I have collected at least a thousand of that stones over the last years.
Let´s approach the question from another way: 1) provenance, volcanic/basaltic rocks are frequent in Earth´s history. As this is a beach pebble, it may be transported 100s of kms. 2) the geological map of Portugal indicates in "northern Portugal" extensive outcrops of basic magmatic rocks, and in the Lusitanian basin some Mesozoic rocks (including Triassic) where sometime basaltic rocks occur. So my question is: where is the beach? Geol. map here: http://www.mindat.org/photo-330110.html
Any iron producing industry in this area? Including historical (medieval/Roman) ones?
It looks like slag, look into the voids (by hand lenses) and maybe provide a detailled photo. Rubb the stone over the base of a coffee mug, describe the color of the powder. If reddish --> iron.
looking at the photos, they look really very similar to the Etruscan (and later Romans) slags that can be found along some beaches in Tuscany (Italy), in the "Tuscan metallogenic province"
I agree with previous answers. It is always difficult, if not impossible, to tell from a photo; but it does look like it contains vesicles. It could be volcanic, but I agree with Reicherter and Montanari; it looks like slag. And since it was found on a beach, who knows where it came from.
The stone does not show any fusion crust, typical for meteorite. It is most probably a basalt. However, does it stick to a magnet?. If yes then you need to make a cut and may be a thin section to see the texture
Klaus, the beach is in Esposende, about 50 Km north of Porto, with the coordinates 41º 32' 52" N and 8º 47' 32" W.
Very interesting approach, yours!
It is curious that, a few years ago, I found in the same beach (maybe 1 or 2 km north) another "alien" rock, but in that case I always thought it was volcanic (density only 2.2 and full of holes.
http://www.ancientportsantiques.com/wp-content/uploads/pdf/AncientPortsVol-I-List.pdf
Dear Jose, you have many nice beaches and many archaeological remains and harbours since Iron Age, but especially Roman times, I have found a harbour in your city, situated directly on the spit in the lower part of your image. The link (above) leads you to a list of Roman harbours. So, a slag from iron production seems likely (for every-day objects and products). However, if it is Roman or later... I can´t tell. Another reference has a little bit of iron industry in the south near Povoa de Varzim. I hope this helped.
Surface features and density do not support being iron meteorite. Vesicles possibly seem to have resulted from removal of foreign weaker impurities that were captured and embedded within once molten iron rich background. I tend to agree with Klaus that the explanation should consider both historical (ancient iron manufacturing) and geological (beach environment, transportation, alteration, etc.) context. I would suggest making a polished section to look at internal textures and composition under reflected light.
I think you need to make thin section to know the mineral composition of the rock, after that the decision may be easier
I feel that apriori if it has a well formed 'fusion crust' it could be meteorite. In addition if a thin section of the same exhibits 'chondrules' it should be a meteorite (chondrite). However a detailed analysis on mineralogy/chemical analysis, would more appropriate before any (final) inference.
I know quite well the geology of Northern Portugal. On the coast there are many outcrops of beach-rocks cemented by ferruginous and manganese crusts. To me this show is a fragment of a crust of iron and manganese rounded by the sea waves. Of course, in my opinion it is neither a meteorite nor a volcanic rock
From the photo it looks like a rounded pebble of a vesicular basalt. As Klaus Reicherter says there are plenty of basaltic outcrops in the Lusitanian basin, so it can have a local origin. Another possibility is a scoria from a lime kiln or from a iron foundry. Doesn't look as iron-manganese crust (as Juan Ramon suggests) to me; usualy those are not as homogeneous as the sample in the photo and quartz grains or pebbles are ususally present.
A thin section would normaly be sufficient to see what it is.
I agree with José Madeira that the best solution is a thin sheet or chemical analysis. But from the photo and samples caught in the area between Caminha and Viana do Castelo and also further north in Galiza (Spain) there are many Quaternary fluvial deposits or even slope deposits with ferruginous levels that marine erosion has rounded. Result in songs that have the same appearance. There are also rounded blocks of volcanic rock but very different. Please see two examples pictures of one another sedimentary rock and volcanic rock (diabase) found on the coast. Left volcanic rigth sedimentary
Dear all
Unfortunately, I regret not having means of getting the thin section, which (and many of you have said) could solve this dilemma (or better, trilemma). Anyway, your answers and discussions have been so interesting and enriching to me, that I almost feel happy about my poor knowledge on that issue.
Particularly, I never thought that my place of residence could be so full of surprises.
Perhaps It doesn't help the discussion, but I took the liberty of attaching the photos of another (in this case, the density is only 2.2) rock found in a very near beach, which I always supposed to be volcanic.
Hi,
Excuse me for butting in but why would anyone think it might be a meteorite just because its dark and rounded and has a few indentations? It's not an iron because the mass/density is far too low. I get several similar sorts of queries here in NZ "we've found a rock, we think it might be meteorite" which invariably turn out to be something commonplace. One person no longer speaks to me because I didn't send his common alluvial pebble (which he was convinced was a meteorite) to Smithsonian to 'have it checked'. Having said that, a recent specimen I was alerted to was more convincing: it was very dense and magnetic, but ultimately not a meteorite.
Regards
David
here, for a comparison, two photos from the net of etrurian slags reworked along the Baratti beach near populonia, Italy
I suggest to study if in that place you have found the pebble there were in the past some metallurgic activities as in Tuscany
I would have thought the magnetic character and much higher densities would separate possible iron meteorite and metallic slag from ordinary rocks.
.
Hi José
You could contact a colleague geologist in the nearest university (Porto, Coimbra, or Braga). Eventually, with the hand specimen they could solve your dobts, maybe even without needing a thin section.
Does not look like a meteorite: --too much vesicles; --no light rounded inclusions in the largest cavities that samples the interior of the rock, and that would indicate chondrules.
If you have a compass, check whether the magnetic needle move in contact with the rock. Michel
The density of the rock indicates that it must be basic volcanic rock. On the basis of megascopic charaters it looks like vesicular basalt. It is better to prepare the thin section and study the microscopic character of the rock specimen
Dear discussion partners, dear Jose,
it would be very helpful to read all discussion points before posting another answer, and avoid moving in circles? Jose: what´s about Jose Madeira´s answer? If not, send it to RWTH Aachen, we will have a look at your beach pebble.
Dear Klaus and colleagues
Thanks for your answer that helped to put things in their proper places.
As I don't know any geologist in the nearby university (it would be the best way, of course - thank you, José Madeira, for the suggestion), I will probably accept your offer and send the rock to Germany.
Let's hope it will not be a total waste of time for you, in Aachen.
Thanks.
most interestin question and specimen José. volcanic vs slag isa problem I have been addressing in simiar Scottish beach deposits for some years now failing to arrive at a specified foundary-provenance I fear that the answer may not become conclusive until you have any geochemical analyses the clast looks ratherwel rounded & the vesicular - wa[l asperities seam softened also which suggets to me that it has been within the sedimentary transport cycle for some time { it would be interesting to know if the context was a find on a pebble beach [ where erosional wave transport rounding would be significant] or stand line on a fine grained beach ?{ where the rounded-form is less likely to have been acquired} I have encountered many albeit more angular fist size pumice blocks on strand-lnes of N Atlantic islands which turned out to be variously carbonaceous slag, alumina rich glassy slags & reworked Holocene pumice from eroding cliff archaeological section contexts > 4000 yrs old. This clast looks very much like slag deposit as suggested by Pedro! it maybe interesting to note the paper of Troll et al [2012] which discusses the restingolite & xenopumices, in submarine eruptives from the Canarian El Hierro volcano further south in the Canarie Islands. Again without geochem the vesicular nature is not enough to prescribe geochemical provenance though to me it does exclude meteor in origin leadng to slag of volcanic . José could you perhaps explain how density was calculated? material or bulk density?[ if volume was determined by water displacement then less accurate values could be yielded if the vesicles do not fully saturate; Does it float?
Floating stones off El Hierro, Canary Islands: xenoliths of pre-island sedimentary origin in the early products of the October 2011 eruption V. R. Troll, et al. [ 2012]
http://www.solid-earth.net/3/97/2012/se-3-97-2012.pdf
Dear John
Thank you very much for your answer and the ideas you shared in it.
About your questions:
a) The beach where I found the strone is somewhat peculiar. It is a sandy one, but with extense layers of peeble stones. These stones are miscellaneous in shape and colour and many of them (seems to me) belong to species very alike of the region of Esposende. For instance, I have been collecting (it is a hobby of mine) hundreds of flint stones and in land I never found this kind of rock.
b) I have determined the value of density in a very simple way. I weighed the rock (52.389 g) and then I introduced it in a 250 mL graduated cylinder with water and measured the difference in the level of water (196 - 178 = 18 mL). The quotient (2.9 g/cm3) give me an approximate value of the density. The rock doesn't float in water.
When I did answer your question, I forgot about an expedition that I did organize (for a group of five colleagues), with the help of the Ministry of Mines and Energy of Morocco. Two colleagues already had a training about collecting meteorites in cold and/or hot deserts. After 4 weeks of walking around, we found....none. The worst trouble was the finding that our exploratory path was polluted while running in the proximity of iron mineral ore deposits, which release stones that look like meteorites. And when you have too much pollution (meaning only one bad rock every 500 meter square) you cannot find a meteorite that are very rare (about 10-20 kg per year for the whole Earth), unless you stand right into an accumulation field of meteorite, such as a stagnant blue ice fields in Antarctica. So, either hunt around for possible iron ore deposits, or conclude that there is no accumulation zone of meteorite around .
Yes, it must have been a rather frustrating search. In my own case, although far from comparable with yours, I am still not sure about what I really found - volcanic rock, iron ore or anything else?
Looking at the images, my first impression is that it may be some type of industrial slag. Reading through the answers, it looks like many have come to the same conclusion. Working in South Wales UK, a region of much past heavy industry, we have many enquiries where material like this is brought in for identification.
In my experience, most of these potential meteorite enquiries have turned out to be slag. On many occasions, this material has been found on a beach. Whether the slag was used as ship ballast, dumped at the coast as coastal defence, or the shore was just a very handy place to dump waste material!
Apologies for my very late answer to this question, I have only just seen it.
All the best,
Thank you Andrew, for your interesting answer. Many ships have passed on that coast, so your explanation seems very plausible.
Best wishes
José
I agree with Andrew. The sample appears to be devoid of a 'fusion crust', this would have erased the vesicles as seen in the present sample.
Clearly slag: Comparable to the non-meteoritic material that littered the N shore of Massachusetts from ships' ballast, and the bedding to the early railroad links across the Green Mts.
First vesicular basalt, slag and meteorite, three of them have suffered high temperature, they all can contain iron. So they have some same features. If clear fusion crust of a meteorite still can be seen, it can help to identify. But it always weathered. The one was found on the beach, the fusion crust (if it had) must have been washed away.
Another feature is the holes. I think the holes are different from the vesicular of slag and basalt. The holes may be embedded chondrules of chondrules or metals which have broken off. So many holes the density is meaningless.
All the best,
On the surface there are some sky-blue substance and reflected colorful light substances which I have seen in meteorites.
You can polish the surface with a cloth, if the bottom and the surface near the holes have reflected colorful light substance. I think it is worth to find a way to make a thin section to see if there are inclusions of crystals.