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In 1978 Pierre Devismes wrote a book Atlas photographique des mineraux d’alluvions (Photographic atlas of detrital minerals). I believe it remains the best illustrated treatise on detrital minerals to this day. Unfortunately I do not own a copy of it. It is out of print and seems to be impossible to purchase. But I do have selected pages of it in scanned format.
There are 641 photographs depicting 183 alluvial minerals. This is really impressive number because I believe you can easily describe 99.99999 percent of the sand grains with 183 mineral species (if we leave out lithic fragments and biogenic grains).
But this is nothing unimaginable. What really strikes me is the number of sand samples/mineral concentrates his work group at BRGM mining division in Nantes described and analysed — 286,088 (most of them from France and collected during 8 years of field works). This number is beyond what I can imagine. I have more than 1,000 sand samples and even this is far more than I can handle. I have superficially looked (with microscope) upon all of them but I have more deeply studied maybe only one hundred or so.
The mineral concentrates shown on the photos of the book are selected from these samples. I don’t know how they identified all the mineral species but it definitely is lots and lots of work that takes enormous time. I wonder if someone now wants to underake writing such a book. How much would it cost? Well, I don’t want to think about that and it may well explain why there are no such books written in the last 30 years.
If such a huge number of samples is studied and a book written based on that, then it is no wonder that the book is out of print and no one considers selling it although it is quite ancient already.
Such a large number of sand samples seems to be a perfect database for some serious statistical conclusions. I am not sure about how much of it this book contains but I have a copy of a table from the book (repeated in another book) where mineral species have been categorized according to their frequency of occurrence in sand.
I hope I won’t commit a serious crime if I repeat part of it (the most common ones) here.
Quartz — essential component
Feldspar — essential component
Mica — very abundant
Tourmaline — very frequent
Staurolite — very frequent
Garnet — very frequent
Zircon — very frequent
Glauconite — very frequent
Magnetite — very frequent
Hematite — very frequent
Ilmenite — very frequent
Rutile — very frequent
Cassiterite — very frequent
Pyroxene — frequent
Sillimanite — frequent
Limonite — frequent
Leucoxene — frequent
Pyrite — frequent
Marcasite — frequent
Anatase — frequent
Monazite — frequent
Siderite — frequent
Amphibole — frequent enough
Epidote — frequent enough
Titanite — frequent enough
Andalusite — frequent enough
Kyanite — frequent enough
Goethite — frequent enough
Spinel — frequent enough
Chromite — frequent enough
Corundum — frequent enough
Apatite — frequent enough
Wolframite — frequent enough
Arsenopyrite — frequent enough
Topaz — frequent enough
Olivine — frequent enough
Perovskite — frequent enough
Xenotime — frequent enough
Columbite-tantalite — frequent enough
Galena — frequent enough
Sphalerite — frequent enough
Cinnabar — frequent enough
Scheelite — frequent enough
Baryte — frequent enough
Beryl — frequent enough
According to Devismes, all other minerals are either rare or very rare in sand.
Agate is a rock type admired by many because of its beauty. Much smaller but still numerous and perhaps more knowledgeable group of people like breccias. Today I want to demonstrate something that should please both of them — agate breccia.
 Agate breccia from the Black Forest, Germany. The width of the hand sample is 12 cm. The hand sample belongs to the Museum of Geology of the University of Tartu. I have no idea what brecciated the rock but I think it is just beautiful.
Few explaining words about the terms used in the title:
Agate is a rock type that is composed of microcrystalline banded quartz and chalcedony. You might say that chalcedony is just a microcrystalline quartz but it is somewhat more complicated. Chalcedony is actually a fibrous intergrowth of quartz and moganite. Hence, it could be considered to be a rock type that is composed of two minerals. The compositions of chalcedony and quartz are still the same: SiO2
Breccia is a coarse-grained rock composed of angular broken fragments of preexisting rocks. Breccias may have very diverse origins.
There is a nice exposure of pillow basalt just by the road that connects the Teide NP in Tenerife to the eastern part of the island. I didn’t know its existence before but when I saw these rocks while driving through the misty cloud forest that surrounds the Teide I knew I have to stop and take a closer look.
I had no doubt that these are pillows. However, there is one annoying aspect that troubled me. This outcrop is approximately 1200…1400 meters above sea level. Why is this a problem? Because pillow basalt forms underwater.
I think there is rather small possibility that these pillows formed in a lake. If we assume that they formed in seawater then there really can not be another explanation that the whole island has been pushed up by more than a kilometer. This is rather remarkable. I thought that oceanic islands grow larger mainly by the addition of new lava and pyroclastic layers. They of course swell also if the volcano is active which Tenerife is, although the most active regions of the Canary Islands at the moment seem to be the western part of the archipelago (La Palma, El Hierro).
But now I know a better explanation. These are not pillows at all. This is just a classic and beautiful example of spheroidal weathering. There are no radial fractures visible which should develop in pillow basalt because of contraction while cooling rapidly and there seem to be no flash-frozen crusts.
However, it is a really nice example of spheroidal weathering. What is the reason that we find it there? First of all, volcanic rocks often weather to smectite clay which expands when wet. Repeated diurnal cycles of taking on and losing water help to form such a weathering pattern. The particular location is especially suitable for that type of weathering because there are lots of moisture — its a cloud forest surrounding the volcano. You will even see fog in the first picture.
 For scale: me...  ...and my wife, Tuul.
Pyrope is a garnet just like almandine and several others.
Easiest way to see what makes the difference between garnet minerals is to take a look at the table below:
| Mineral |
Composition |
Group |
| Pyrope |
Mg3Al2(SiO4)3 |
Pyralspite |
| Almandine |
Fe3Al2(SiO4)3 |
Pyralspite |
| Spessartine |
Mn3Al2(SiO4)3 |
Pyralspite |
So, pyrope is a magnesium garnet, almandine is an iron garnet, and spessartine is a manganese garnet. Note that most natural minerals are mixtures of the three (dominantly mixtures between pyrope and almandine or almandine and spessartine). Absolutely pure endmembers don’t exist in nature anyway but solid solutions in garnets are really common. Actually, pure pyrope endmember is really rare. Most commonly up to 70% of the sites in crystal lattice that are shared between Fe, Mg, and Mn are occupied by Mg in pyrope. The composition of garnet may be expressed the following way: Py62 Al35 Sp3. Mineral with such a composition is called pyrope. To make things more complicated, other chemical elements may also enter the crystal structure. Chromium, for example, is especially common in pyrope.
These three minerals are collectively called pyralspites (pyrope + almandine + spessartine). We need this term because there are more garnets than these three mentioned above.The rest of the garnet group minerals are somewhat different. They are called ugradites (uvarovite + grossular + andradite). There are no continuous solid solution between the two groups. Therefore, I will not pay attention to the ugrandite group now. There are even more garnet varieties possible but these are really rare and have no geological significance.
I also don’t want to write more about the pyralspites in general anymore because I intended to write about pyrope here. However, I think that such a lengthy introduction is needed to give a proper background upon which we can build our understanding of these remarkably beautiful minerals that are quite common in many different rock types and sand as well.
All pyralspite minerals are shade of red — light pink, yellowish red, red, purple, very dark red (almost black) are the most common possibilities. The color depends on the grain size. They all tend to be lighter in sand and darker as large grains (this is universal among minerals). But the color also depends on the composition. Pyrope is the darkest of the three. It is usually dark red, purple, or almost black.
Unfortunately, color only is not a reliable guide. Perhaps more useful is to know from what type of rocks are these minerals coming from. Almandine is the most common of the three and it comes mostly from metamorphic rocks (garnet schist, garnet amphibolite). Spessartine comes from igneous rocks like granite and pegmatite. Pyrope comes from ultramafic rocks (peridotite, pyroxenite, kimberlite, and serpentinites derived from them) or ultrahigh pressure metamorphic rock eclogite.
Pyrope is a semi-precious gemstone partly because of its beautiful dark red color and partly because it is much rarer than almandine. It is rare, of course, on the upper part of the crust. The rocks containing pyrope are not rare at all deep below.
Pyrope is one of the index minerals in diamond prospecting. It does occur together with diamond in kimberlite pipes. Pyrope is not a typical kimberlite mineral but kimberlite pipes often contain pyrope-bearing blocks as xenoliths. These diamond containing pipes are small and hard to find. Pyrope grains found in river sand might indicate that ultramafic rocks could be somewhere near. Prospectors just need to go upstream and take samples until they find no pyrope anymore. Then, if they are lucky, diamond bearing kimberlite pipe could be nearby.
Here are picture of pyrope grains and some photos of almandine grains as well to compare the color. Unfortunately I don’t have a photo of spessartine grains at the moment. They occur in my sand samples, I have no doubt about that. I often find yellowish garnet grains that could be spessartine but so far I have not had an opportunity to determine their composition. So, I prefer not to just guess blindly. Color, after all, is often badly misleading indicator.
 Pyrope grains from peridotitic rocks from the Czech Republic (The Bohemian garnets). The width of the view is 20 mm.  Almandine grains from Redondo Beach, California, USA. The width of the view is 10 mm.  Almandine grains from Emerald Creek, Idaho, USA. The width of the view is 15 mm.  Garnet peridotite from Alpe Arami, Ticino, Switzerland. Purple crystals are pyrope, green is probably chromian diopside and yellow is olivine. The width of the hand sample is 9 cm. The hand sample belongs to the Museum of Geology of the University of Tartu.
Callan Bentley wrote about a xenobomb which is an aggregate of olivine in a basaltic rock.
I also have similar photos of a similar rock. My sample is from Lanzarote, The Canary Islands. It is a xenolith of a dunite? As a mineral aggregate this green stuff in basalt definitely qualifies as a dunite but I was not sure whether it comes as a xenolith from the mantle or is it an olivine cumulate rock formed in the crust. Hence, my question was: is it necessary for a dunite to form deep below or do we only need the rock to be phaneritic and composed of more than 90% olivine? I tend to think its a xenolith because it seems to be surrounded by basalt from every direction.
I got few responses. The consensus seems to be that the rock must be >90% olivine to qualify. I think its a reasonable way to look at it because we often really don’t know and can’t possibly know how a particular rock sample came to be. The Canary Islands, for example, have bneen extensively studied. It is clear that there are very complex interactions and the source(s) of the ultramafic rocks remain often uncertain. Dunite inclusions may be foreign to the host carrier (xenolith) or there might be a genetic link (inclusion).
Here are the pictures of the same rock from different angles:
 Dunite xenolith in basalt from Lanzarote. The width of the hand sample is 9 cm.  Dunite xenolith in basalt from Lanzarote. The width of the hand sample is 11 cm. I have written about somewhat similar rock before: Olivine basalt from Oahu.
Callan Bentley and Robin Rohrback-Schiavone have gigapanned two more sand samples: pyrite sand and actinolite sand. Thanks!
The first one contains pyrite and silicate grains from Cyprus. The second one is from Ontario, Canada. I have already written about this sample: Actinolite sand from Ontario.
I also have to make a small correction. The sand sample with pyrite contains more than just pyrite and goethite. It seems to me that I made a mistake when packing these sands and sent the wrong sample. They are from the same place but with somewhat different composition. The other one I planned to send contained beautiful pyrite cubes, some of them with goethitic/limonitic cover but in this gigapan you also see green silicate grains. I am not sure but they could be epidote grains.
I also recommend to check a gigapan of olivine sand. There are lots of very beautiful bright green olivine grains.
Dikes are sheetlike igneous intrusions. We usually see them in two dimensions but sometimes they form prominent threedimensional landforms.
Here is a photo of a dike I saw while spending a vacation in Tenerife. I didn’t have an opportunity to stop there and inspect it more closely. Even the photo is taken while driving but it should be understandable that this dike forms really impressive wall. The photo is taken inside the Las Cañadas caldera which surrounds the Mount Teide which is a highest volcano in Europe and second overall only after the volcanoes of Hawaii (Mauna Loa and Mauna Kea). I mean measured from the base of the mountain which is kilometers beneath the waves.
How is it possible that such thing survived the caldera collapse? Well, the caldera there is a bit unusual. It is not a depression of a vertical collapse. It was more like an enormous landslide. I don’t know for sure but probably the dike which is almost perpendicular to the caldera wall right behind it (and therefore more or less parallel to the direction of landslide) just survived the event and was later preserved better than the surrounding rocks because it is made of hard rock, not loose pyroclastic material.
I have also written about syncline in 3D and another interesting landform in the Las Cañadas caldera which is claimed by some to be the most photographed rock in the world — The Cinchado.
 Dike in the Las Cañadas caldera in Tenerife, The Canary Islands.
My home country Estonia has been geologically quiet place for a loooooong time.
I usually think its a bad thing. No volcanoes, no mountains, little mineralogical and lithological versatility, no real structures — everything is more or less parallel and layered. The sedimentary layers that cover the crystalline basement have never been buried very deep. Maximum perhaps 1 km or so. Therefore, these sedimentary rocks are only weakly altered by diagenetic processes. Because of that we have something rather remarkable. We have a layer (up to 70 meters in thickness) of bluish gray clay in the bedrock that is half a billion years old (from the Cambrian). I really mean clay, not claystone. This clay is still quite soft and becomes muddy when wet.
Here is a photo of this clay with mud cracks. The mud cracks are fresh but the clay itself is really old. The photo is taken in a clay quarry. The clay is used to make cement.
 Recent mud cracks in Cambrian clay.
Dunite is an ultramafic plutonic rock that is composed almost exclusively of olivine.
I wanted to take this sentence apart to make it understandable to everyone but then I discovered that I started to write lengthy paragraphs about ultramafic rocks in general, not about dunite in particular. So, I will leave that material for a separate post now. Very shortly: ‘ultramafic’ means that mafic minerals form more than 90% on the rocks composition. Most common mafic minerals in ultramafic rocks are definitely pyroxenes and olivine (if hornblende is present it is added to pyroxenes). Rocks that contain more than 40% olivine are peridotites. Note that this 40% means 40% of olivine-pyroxene(hornblende) pair, all other minerals are excluded in current classification scheme. Peridotite that contains more than 90% olivine have a special name, they are called dunite (named in 1864 after Dun mountain in New Zealand).
‘Plutonic’ means that the rock is not volcanic, it didn’t form at or near the surface. In the case of dunite the formation place was probably very deep in the mantle. That’s why it is so rare on the surface. Dunite is rare but it is pretty. However, its beauty is not the reason to reserve a separate rock name for it. It is an important rock type because it is probably very common in the mantle.
Dunite is mostly composed of olivine which is a bright green mineral. Fresh dunite is green as well. However, olivine readily alters and loses its bright green color pretty quickly. Chances are very high that on the way up in the crust olivine grains lost some of its brightness. Hence, many dunite samples look dull yellow, not green anymore. Dunite usually contains chromite (Mg-bearing spinel group mineral). However, if the most common spinel mineral is magnetite, dunite is named olivinite instead.
Magnesium is a very common chemical element in the mantle. Therefore, we should expect to see lots of unusual mineral varieties in dunite. I already mentioned chromite but Mg-bearing garnet pyrope is quite common as well. If the dunite sample contains significant amount of garnet, then it should be added to its name. The rock sample below is a garnet peridotite because it contains one very large and several smaller purplish pyrope crystals. It is probably not true dunite because it contains more than 10% chromian diopside (bright green mineral). It should be named either wehrlite (if there is almost no orthopyroxene) or lherzolite (more than 10% orthopyroxene).
 Garnet peridotite from Alpe Arami, Ticino, Switzerland. Purple crystals are pyrope, green is probably chromian diopside and yellow is olivine. The width of the hand sample is 9 cm. The hand sample belongs to the Museum of Geology of the University of Tartu. Dunite xenolith in basalt from Lanzarote. The width of the hand sample is 9 cm.  Dunite with fresh olivine grains. Photo: Ron Schott.
Gigapanning is very useful technology in geology because it allows us to first get a general overview and then zoom in to see smaller structures. It is already used extensively by some members of the geoblogosphere. Thanks to their work we have seen many outcrops in such a detail that was unimaginable before.
I was interested to see how useful are gigapans in sand photography. Callan Bentley kindly offered to gigapan some of my sand samples. Here are two of them. I much prefer to watch gigapans in full screen. Unfortunately I can’t find a way to add such a feature to my website. To do that you probably just have to go directly to the gigapans website. Here are the links to these gigapans: gigapan.org/gigapans/98519 and gigapan.org/gigapans/98542.
The first one is from the La Paree Beach, Bretignolles-sur-Mer, France. The second one is from the Calvert Cliffs State Park, Soloman Islands, Maryland, USA. I am very pleased with the first one. The sand is interesting and beautiful and it shows its beauty and versatility quite well. I was afraid that these sands are perhaps too fine-grained but it doesn’t seem to be the case. The gigapans are sharp enough, almost comparable to the microscope view. The second gigapan is not as good. Probably because it is a mixture of transparent quartz and black ilmenite which need different exposure time. There are enough light for quartz but not enough for dark ilmenite. This is a common problem in macro photography if you have to take photos of light and dark objects at the same time.
There are several things that I like about these gigapans. It is good that I can first see the sand as I would see it with the naked eye and then smoothly zoom in to acquire microscope view. I’ve been thinking about that before when I show sand photos taken with macro lenses. These pictures may be pretty but they are somewhat detached from the reality. People who look them do not understand how this sand looks to them if they see it in a beach. This problem is eliminated here.
Taking macrophotos of sand is usually lots of work. I study sand under the stereomicroscope but I do take photos with camera and macro lens. Thus, I can not take a photo as soon as I spot something interesting. Sand grains are very small which means that the grains I was interested in are usually very hard or impossible to find with the camera. So, I just take a photo and hope that it has something interesting there. Usually it is not as good as I had hoped because one photo covers very small area. It is different with gigapans because they are composed of many photos. I can search large area and choose between many grains and take a snapshots of the best to illustrate my blog posts for example.
The results are very promising and I am sure that gigapanning will be much more widely used by geologists in the future although currently it is rather expensive and unfortunately affordable to research institutions only.
Breccia is a clastic rock composed of angular rock fragments which are held together by a cement. There are several ways how breccias form. One of them (quite rare) are impact events. Meteorite explosion vaporizes lots of material but it also shatters the bedrock that is far enough to escape vaporization but is near enough to be severely hit. Such rocks are full of fractures but they still stay together and as time goes by they become one integral rock again.
The rock below is an impact breccia from Germany. The brecciation took place 14 million years ago during the impact event that created the Nördlinger-Ries meteorite crater. The clasts are composed of silicified pieces of former carbonate rock, possibly limestone. They are held together by a silica cement.
I have written about the Ries crater and its rocks before: Houses built from diamonds and impact breccia
 Impact breccia from the Ries crater, Germany. The width of the rock is 14 cm. The hand sample belongs to the Museum of Geology of the University of Tartu.
I recently posted a picture of migmatite from Norway. Today I am itching to post another one. These rocks are really beautiful and fortunately very common in certain areas and versatile as well.
Where can we expect to find such rocks? They form deep in the crust where rocks are ductile because of enormous pressure and high temperature. Such conditions prevail under the forming mountain ranges where crust is thicker than usually. Mountains eventually erode away and rocks that were formed deep in the crust become exposed. So, if we see migmatite or gneiss, we can pretty safely say that big mountains once stood here. Migmatites are usually very old because it takes time to completely wear away mountains. Norway is a mountainous country but this migmatite didn’t form during the Caledonian orogeny (approximately 400…500 Ma) which is mostly responsible for the mountainous terrain in Norway. These mountains are still there and we have to wait few hundred million years more to see the migmatites that formed underneath them. The migmatite or migmatized gneiss I am presenting today formed one billion years before. Its age could be anywhere between 1.8…1.5 billion years. It is part of a Norwegian basement in western part of the country which is not covered by allochthonous rocks.
 This migmatized gneiss is collected in Norway (near Hornindal). It is only 8 cm across. The hand sample belongs to the Museum of Geology of the University of Tartu.
Zircon is a zirconium-bearing silicate mineral (ZrSiO 4).
Zircon is very interesting and useful mineral in several ways. It is unique mineral because it is mined for several reasons. It is a principal source of zirconium and hafnium (zircon always contains small amount of hafnium which replaces zirconium) and contains yet smaller amount of rare earth elements too. But zircon is also an industrial mineral. Its useful properties are extremely high melting temperature and strong resistance to chemical attack.
Zircon is very important mineral to geologists. Small amount of zirconium is replaced with uranium which is a radioactive element. We know the half-life of uranium and can therefore calculate the age of zircon crystals. But this is not all. Zircon is used in geochemical studies to determine magmatic sources (mantle vs crustal) and composition of magma it crystallized from among several other applications.
Zircon is relatively little known despite being so important. Perhaps because it is rare? Actually not, zircon is a very common mineral. Zircon is originally igneous mineral but it is hard and very resistant to alteration and weathering. Hence, it occurs in metamorphic and sedimentary rocks as well. The problem with zircon is the size of crystals — they are very small, almost invisible. Hence, large crystals are valued gemstones which are named “hyacinth”.
Why is zircon so small? Common magmatic minerals like feldspars, pyroxenes, etc. want to know nothing about zirconium (chemical element). So large cation simply won’t fit into their crystal structure. So, poor zirconium finds no one to play with and has to form its very own silicate mineral which we know as zircon. The crystallization starts more or less simultaneously in very many spots but zirconium is not particularly common chemical element. There is simply not enough material to grow large crystals. Hence, we find zircon often but the crystals are really microscopic and often entirely surrounded by other minerals which have later grown around already formed zircons.
Zircon grains are the oldest terrestrial material we have found so far. Oldest zircon grains are 4.40 billion years old which is pretty good result (The Earth itself is about 4.54 billion years old).
Zircon is a very common mineral in sand. Zircon grains are small but they are still often easily spotted. Euhedral grains (tetragonal prisms with dipyramidal terminations) are especially characteristic but all zircon grains tend to have dark band parallel to the outer edge (because of high refraction index). This is seen under the microscope if the grains are illuminated from below the sample (light goes through the grains).
 Large zircon crystal (18 mm) from the Ural Mountains, Russia. Large zircon crystals are valued as gemstones (yelloish gem zircons are usually called "hyacinth"). The sample belongs to the Museum of Geology of the University of Tartu.  Samples of zircon concentrates from India (on the left), USA, South Africa, and Australia. Note that there are slight color differences but generally zircons are light-colored or colorless. There are 4 square centimeters of sand on every square-shaped photo.  Zircon concentrate from South Africa. Zircons are either rounded and slightly elongated or form clearly elongated teragonal prisms with dipyramidal terminations. The width of the view is only 3.1 mm.
Article about the hydrothermal processes went online without any illustrations. It is not a paradigm shift of this blog. I still believe in photos and will continue to use them. I just didn’t have anything appropriate at the moment.
But now I have a nice photo of hydrothermally altered granite from Norway. There is a green vein in granite. One could argue that it is some sort of dike or something similar but take a closer look. There are some unaltered red feldspars and of course quartz (gray) which is very resistant mineral to all sort of changes. Dark minerals are the most reactive and they are mostly gone.
It is obvious that the green vein was granite but its mineralogy somehow changed. It is mineral epidote that gives greenish color to the vein. Epidote is a common mineral in hydrthermally altered rocks. It is quite common in granite. Such epidotized granites are sometimes named unakite and valued as semi-precious gemstones. Why is this vein in granite? Perhaps because there were some sort of weakness, most likely microscopic crack(s) that allowed hydrothermal fluids to infiltrate the rock.
 Hydrothermally altered granite from Evje, Norway. The width of the view is 6 cm. The hand sample belongs to the Museum of Geology of the University of Tartu.
Monazite is a phosphate mineral containing rare earth metals (Ce,La,Th)PO 4. These rare earths or lanthanides can substitute each other in the crystal structure of monazite. There are more lanthanides that can enter the lattice, these three are the most common.
Monazite mostly crystallize out of magma (granite, syenite, pegmatite, carbonatite) but it occurs in several metamorphic rocks as well. Monazite is resistant to weathering, it is therefore common mineral in sand. However, monazite grains are usually very small, they are therefore not easy to spot. Why are they small? The reason is the chemical composition of monazite. Lanthanides are chemical elements that are required for the monazite to form. These elements are not wanted by more common minerals because lanthanides do not fit into their crystal structure. Hence, there is little competition and the crystallization centers of monazite form in many places. However, these elements are still pretty rare and there simply is not enough material for the large crystals to form.
Monazite grains in sand are usually yellow, reddish, or brown. They are mostly rounded and slightly elongated.
Monazite is an important mineral resource, it is one of two minerals that are mined for their rare earth content, the other being bastnäsite which is even more important as a source of lanthanides but not as common in sand. Monazite is mined from sand, mostly beach sand.
Rare earth metals are produced almost exclusively in China. I am not sure about the current situation but about a year ago there were only two countries (according to newspaper article, I am not sure whether it is correct) in the whole world that produced lanthanides. China produced 98% and what was the other country that produced the remaining 2 percent? It is Estonia where I live but as much as I know monazite is not used here as raw material of rare earth metals.
 Monazite concentrate from North Carolina, USA. The width of the view is 3 mm.
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