Neodymium is a chemical element with symbol Nd and atomic number 60. It is a soft silvery metal. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach, it is present in significant quantities in the ore minerals bastnäsite. Neodymium is not found in metallic form or unmixed with other lanthanides, it is refined for general use. Although neodymium is classed as a rare earth, it is a common element, no rarer than cobalt, nickel, or copper, is distributed in the Earth's crust. Most of the world's commercial neodymium is mined in China. Neodymium compounds were first commercially used as glass dyes in 1927, they remain a popular additive in glasses; the color of neodymium compounds—due to the Nd3+ ion—is a reddish-purple but it changes with the type of lighting, due to the interaction of the sharp light absorption bands of neodymium with ambient light enriched with the sharp visible emission bands of mercury, trivalent europium or terbium. Some neodymium-doped glasses are used in lasers that emit infrared with wavelengths between 1047 and 1062 nanometers.
These have been used in extremely-high-power applications, such as experiments in inertial confinement fusion. Neodymium is used with various other substrate crystals, such as yttrium aluminium garnet in the Nd:YAG laser; this laser emits infrared at a wavelength of about 1064 nanometers. The Nd:YAG laser is one of the most used solid-state lasers. Another important use of neodymium is as a component in the alloys used to make high-strength neodymium magnets—powerful permanent magnets; these magnets are used in such products as microphones, professional loudspeakers, in-ear headphones, high performance hobby DC electric motors, computer hard disks, where low magnet mass or strong magnetic fields are required. Larger neodymium magnets are used in generators. Neodymium, a rare-earth metal, was present in the classical mischmetal at a concentration of about 18%. Metallic neodymium has a bright, silvery metallic luster, but as one of the more reactive lanthanide rare-earth metals, it oxidizes in ordinary air.
The oxide layer that forms peels off, exposing the metal to further oxidation. Thus, a centimeter-sized sample of neodymium oxidizes within a year. Neodymium exists in two allotropic forms, with a transformation from a double hexagonal to a body-centered cubic structure taking place at about 863 °C. Neodymium metal tarnishes in air and it burns at about 150 °C to form neodymium oxide: 4 Nd + 3 O2 → 2 Nd2O3Neodymium is a quite electropositive element, it reacts with cold water, but quite with hot water to form neodymium hydroxide: 2 Nd + 6 H2O → 2 Nd3 + 3 H2 Neodymium metal reacts vigorously with all the halogens: 2 Nd + 3 F2 → 2 NdF3 2 Nd + 3 Cl2 → 2 NdCl3 2 Nd + 3 Br2 → 2 NdBr3 2 Nd + 3 I2 → 2 NdI3 Neodymium dissolves in dilute sulfuric acid to form solutions that contain the lilac Nd ion; these exist as a 3+ complexes: 2 Nd + 3 H2SO4 → 2 Nd3+ + 3 SO2−4 + 3 H2 Neodymium compounds include halides: neodymium fluoride. Occurring neodymium is a mixture of five stable isotopes, 142Nd, 143Nd, 145Nd, 146Nd and 148Nd, with 142Nd being the most abundant, two radioisotopes, 144Nd and 150Nd.
In all, 31 radioisotopes of neodymium have been detected as of 2010, with the most stable radioisotopes being the occurring ones: 144Nd and 150Nd. All of the remaining radioactive isotopes have half-lives that are shorter than eleven days, the majority of these have half-lives that are shorter than 70 seconds. Neodymium has 13 known meta states, with the most stable one being 139mNd, 135mNd and 133m1Nd; the primary decay modes before the most abundant stable isotope, 142Nd, are electron capture and positron decay, the primary mode after is beta minus decay. The primary decay products before 142Nd are element Pr isotopes and the primary products after are element Pm isotopes. Neodymium was discovered by Baron Carl Auer von Welsbach, an Austrian chemist, in Vienna in 1885, he separated neodymium, as well as the element praseodymium, from a material known as didymium by means of fractional crystallization of the double ammonium nitrate tetrahydrates from nitric acid, while following the separation by spectroscopic analysis.
The name neodymium is derived from the Greek words neos and didymos, twin. Double nitrate crystallization was the means of commercial neodymium purification until the 1950s. Lindsay Chemical Division was the first to commercialize large-scale ion-exchange purification of neodymium. Starting in the 1950s, high purity
Mohs scale of mineral hardness
The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, some of which are more quantitative; the method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones, c. 300 BC, followed by Pliny the Elder in his Naturalis Historia, c. 77 AD. While facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting. Despite its lack of precision, the Mohs scale is relevant for field geologists, who use the scale to identify minerals using scratch kits; the Mohs scale hardness of minerals can be found in reference sheets. Mohs hardness is useful in milling, it allows assessment of.
The scale is used at electronic manufacturers for testing the resilience of flat panel display components. The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly; the samples of matter used by Mohs are all different minerals. Minerals are chemically pure solids found in nature. Rocks are made up of one or more minerals; as the hardest known occurring substance when the scale was designed, diamonds are at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5. "Scratching" a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye. Materials that are lower on the Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number.
While these microscopic dislocations are permanent and sometimes detrimental to the harder material's structural integrity, they are not considered "scratches" for the determination of a Mohs scale number. The Mohs scale is a purely ordinal scale. For example, corundum is twice as hard as topaz; the table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate has a hardness of 7.0. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale; the table below incorporates additional substances that may fall between levels: Comparison between hardness and hardness: Mohs hardness of elements is taken from G. V. Samsonov in Handbook of the physicochemical properties of the elements, IFI-Plenum, New York, USA, 1968. Cordua, William S. "The Hardness of Minerals and Rocks". Lapidary Digest, c. 1990
Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent; the birefringence is quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are birefringent, as are plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking different paths; this effect was first described by the Danish scientist Rasmus Bartholin in 1669, who observed it in calcite, a crystal having one of the strongest birefringences. However it was not until the 19th century that Augustin-Jean Fresnel described the phenomenon in terms of polarization, understanding light as a wave with field components in transverse polarizations. A mathematical description of wave propagation in a birefringent medium is presented below.
Following is a qualitative explanation of the phenomenon. The simplest type of birefringence is described as uniaxial, meaning that there is a single direction governing the optical anisotropy whereas all directions perpendicular to it are optically equivalent, thus rotating the material around this axis does not change its optical behavior. This special direction is known as the optic axis of the material. Light propagating parallel to the optic axis is governed by a refractive index no. Light whose polarization is in the direction of the optic axis sees an optical index ne. For any ray direction there is a linear polarization direction perpendicular to the optic axis, this is called an ordinary ray. However, for ray directions not parallel to the optic axis, the polarization direction perpendicular to the ordinary ray's polarization will be in the direction of the optic axis, this is called an extraordinary ray. I.e. when unpolarized light enters an uniaxial birefringent material it is split into two beams travelling different directions.
The ordinary ray will always experience a refractive index of no, whereas the refractive index of the extraordinary ray will be in between no and ne, depending on the ray direction as described by the index ellipsoid. The magnitude of the difference is quantified by the birefringence: Δ n = n e − n o; the propagation of the ordinary ray is described by no as if there were no birefringence involved. However the extraordinary ray, as its name suggests, propagates unlike any wave in a homogenous optical material, its refraction at a surface can be understood using the effective refractive index. However it is in fact an inhomogeneous wave whose power flow is not in the direction of the wave vector; this causes an additional shift in that beam when launched at normal incidence, as is popularly observed using a crystal of calcite as photographed above. Rotating the calcite crystal will cause one of the two images, that of the extraordinary ray, to rotate around that of the ordinary ray, which remains fixed.
When the light propagates either along or orthogonal to the optic axis, such a lateral shift does not occur. In the first case, both polarizations see the same effective refractive index, so there is no extraordinary ray. In the second case the extraordinary ray propagates at a different phase velocity but is not an inhomogeneous wave. A crystal with its optic axis in this orientation, parallel to the optical surface, may be used to create a waveplate, in which there is no distortion of the image but an intentional modification of the state of polarization of the incident wave. For instance, a quarter-wave plate is used to create circular polarization from a linearly polarized source; the case of so-called biaxial crystals is more complex. These are characterized by three refractive indices corresponding to three principal axes of the crystal. For most ray directions, both polarizations would be classified as extraordinary rays but with different effective refractive indices. Being extraordinary waves, the direction of power flow is not identical to the direction of the wave vector in either case.
The two refractive indices can be determined using the index ellipsoids for given directions of the polarization. Note that for biaxial crystals the index ellipsoid will not be an ellipsoid of revolution but is described by three unequal principle refractive indices nα, nβ and nγ, thus there is no axis. Although there is no axis of symmetry, there are two optical axes or binormals which are defined as directions along which light may propagate without birefringence, i.e. directions along which the wavelength is independent of polarization. For this reason, birefringent materials with three distinct refractive indices are called biaxial. Additionally, there are two distinct axes known as optical ray axes or biradials along which the group velocity of the light is independent of polarization; when an arbitrary beam of light strikes the surface of a b
A crystal or crystalline solid is a solid material whose constituents are arranged in a ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations; the scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification; the word crystal derives from the Ancient Greek word κρύσταλλος, meaning both "ice" and "rock crystal", from κρύος, "icy cold, frost". Examples of large crystals include snowflakes and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most metals, rocks and ice. A third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever.
Examples of amorphous solids include glass and many plastics. Despite the name, lead crystal, crystal glass, related products are not crystals, but rather types of glass, i.e. amorphous solids. Crystals are used in pseudoscientific practices such as crystal therapy, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements; the scientific definition of a "crystal" is based on the microscopic arrangement of atoms inside it, called the crystal structure. A crystal is a solid where the atoms form a periodic arrangement.. Not all solids are crystals. For example, when liquid water starts freezing, the phase change begins with small ice crystals that grow until they fuse, forming a polycrystalline structure. In the final block of ice, each of the small crystals is a true crystal with a periodic arrangement of atoms, but the whole polycrystal does not have a periodic arrangement of atoms, because the periodic pattern is broken at the grain boundaries.
Most macroscopic inorganic solids are polycrystalline, including all metals, ice, etc. Solids that are neither crystalline nor polycrystalline, such as glass, are called amorphous solids called glassy, vitreous, or noncrystalline; these have no periodic order microscopically. There are distinct differences between crystalline solids and amorphous solids: most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does. A crystal structure is characterized by its unit cell, a small imaginary box containing one or more atoms in a specific spatial arrangement; the unit cells are stacked in three-dimensional space to form the crystal. The symmetry of a crystal is constrained by the requirement that the unit cells stack with no gaps. There are 219 possible crystal symmetries, called crystallographic space groups; these are grouped into 7 crystal systems, such as hexagonal crystal system. Crystals are recognized by their shape, consisting of flat faces with sharp angles.
These shape characteristics are not necessary for a crystal—a crystal is scientifically defined by its microscopic atomic arrangement, not its macroscopic shape—but the characteristic macroscopic shape is present and easy to see. Euhedral crystals are those with well-formed flat faces. Anhedral crystals do not because the crystal is one grain in a polycrystalline solid; the flat faces of a euhedral crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal: they are planes of low Miller index. This occurs; as a crystal grows, new atoms attach to the rougher and less stable parts of the surface, but less to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. One of the oldest techniques in the science of crystallography consists of measuring the three-dimensional orientations of the faces of a crystal, using them to infer the underlying crystal symmetry.
A crystal's habit is its visible external shape. This is determined by the crystal structure, the specific crystal chemistry and bonding, the conditions under which the crystal formed. By volume and weight, the largest concentrations of crystals in the Earth are part of its solid bedrock. Crystals found in rocks range in size from a fraction of a millimetre to several centimetres across, although exceptionally large crystals are found; as of 1999, the world's largest known occurring crystal is a crystal of beryl from Malakialina, Madagascar, 18 m long and 3.5 m in diameter, weighing 380,000 kg. Some crystals have formed by magmatic and metamorphic processes, giving origin to large masses of crystalline rock; the vast majority of igneous rocks are formed from molten magma and the degree of crystallization depends on the conditions under which they solidified. Such rocks as granite, which have cooled slowly and under great pressures, have crystallized.
The thermal conductivity of a material is a measure of its ability to conduct heat. It is denoted by k, λ, or κ. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals have high thermal conductivity and are efficient at conducting heat, while the opposite is true for insulating materials like Styrofoam. Correspondingly, materials of high thermal conductivity are used in heat sink applications and materials of low thermal conductivity are used as thermal insulation; the reciprocal of thermal conductivity is called thermal resistivity. The defining equation for thermal conductivity is q = − k ∇ T, where q is the heat flux, k is the thermal conductivity, ∇ T is the temperature gradient; this is known as Fourier's Law for heat conduction. Although expressed as a scalar, the most general form of thermal conductivity is a second-rank tensor. However, the tensorial description only becomes necessary in materials.
Consider a solid material placed between two environments of different temperatures. Let T 1 be the temperature at x = 0 and T 2 be the temperature at x = L, suppose T 2 > T 1. A possible realization of this scenario is a building on a cold winter day: the solid material in this case would be the building wall, separating the cold outdoor environment from the warm indoor environment. According to the second law of thermodynamics, heat will flow from the hot environment to the cold one in an attempt to equalize the temperature difference; this is quantified in terms of a heat flux q, which gives the rate, per unit area, at which heat flows in a given direction. In many materials, q is observed to be directly proportional to the temperature difference and inversely proportional to the separation: q = − k ⋅ T 2 − T 1 L; the constant of proportionality k is the thermal conductivity. In the present scenario, since T 2 > T 1 heat flows in the minus x-direction and q is negative, which in turn means that k > 0.
In general, k is always defined to be positive. The same definition of k can be extended to gases and liquids, provided other modes of energy transport, such as convection and radiation, are eliminated. For simplicity, we have assumed here that the k does not vary as temperature is varied from T 1 to T 2. Cases in which the temperature variation of k is non-negligible must be addressed using the more general definition of k discussed below. Thermal conduction is defined as the transport of energy due to random molecular motion across a temperature gradient, it is distinguished from energy transport by convection and molecular work in that it does not involve macroscopic flows or work-performing internal stresses. Energy flow due to thermal conduction is classified as heat and is quantified by the vector q, which gives the heat flux at position r and time t. According to the second law of thermodynamics, heat flows from high to low temperature. Hence, it reasonable to postulate that q is proportional to the gradient of the temperature field T, i.e. q = − k ∇ T, where the constant of proportionality, k > 0, is the thermal conductivity.
This is called Fourier's law of heat conduction. In actuality, it is not a law but a definition of thermal conductivity in terms of the independent physical quantities q and T; as such, its usefulness depends on the ability to determine k for a given material under given conditions. Note that k
Glass is a non-crystalline, amorphous solid, transparent and has widespread practical and decorative uses in, for example, window panes and optoelectronics. The most familiar, the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica, the primary constituent of sand; the term glass, in popular usage, is used to refer only to this type of material, familiar from use as window glass and in glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of 75% silicon dioxide, sodium oxide from sodium carbonate, calcium oxide called lime, several minor additives. Many applications of silicate glasses derive from their optical transparency, giving rise to their primary use as window panes. Glass will transmit and refract light. Glass can be coloured by adding metallic salts, can be painted and printed with vitreous enamels; these qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows.
Although brittle, silicate glass is durable, many examples of glass fragments exist from early glass-making cultures. Because glass can be formed or moulded into any shape, it has been traditionally used for vessels: bowls, bottles and drinking glasses. In its most solid forms it has been used for paperweights and beads; when extruded as glass fiber and matted as glass wool in a way to trap air, it becomes a thermal insulating material, when these glass fibers are embedded into an organic polymer plastic, they are a key structural reinforcement part of the composite material fiberglass. Some objects were so made of silicate glass that they are called by the name of the material, such as drinking glasses and eyeglasses. Scientifically, the term "glass" is defined in a broader sense, encompassing every solid that possesses a non-crystalline structure at the atomic scale and that exhibits a glass transition when heated towards the liquid state. Porcelains and many polymer thermoplastics familiar from everyday use are glasses.
These sorts of glasses can be made of quite different kinds of materials than silica: metallic alloys, ionic melts, aqueous solutions, molecular liquids, polymers. For many applications, like glass bottles or eyewear, polymer glasses are a lighter alternative than traditional glass. Silicon dioxide is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, branching rootlike structures called fulgurites. Fused quartz is a glass made from chemically-pure silica, it has excellent resistance to thermal shock, being able to survive immersion in water while red hot. However, its high melting temperature and viscosity make it difficult to work with. Other substances are added to simplify processing. One is sodium carbonate; the soda makes the glass water-soluble, undesirable, so lime, some magnesium oxide and aluminium oxide are added to provide for a better chemical durability. The resulting glass is called a soda-lime glass. Soda-lime glasses account for about 90% of manufactured glass.
Most common glass contains other ingredients to change its properties. Lead glass or flint glass is more "brilliant" because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion and was used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern eyeglasses. Iron can be incorporated into glass to absorb infrared radiation, for example in heat-absorbing filters for movie projectors, while cerium oxide can be used for glass that absorbs ultraviolet wavelengths; the following is a list of the more common types of silicate glasses and their ingredients and applications: Fused quartz called fused-silica glass, vitreous-silica glass: silica in vitreous, or glass, form. It has low thermal expansion, is hard, resists high temperatures, it is the most resistant against weathering. Fused quartz is used for high-temperature applications such as furnace tubes, lighting tubes, melting crucibles, etc.
Soda-lime-silica glass, window glass: silica + sodium oxide + lime + magnesia + alumina. Is transparent formed and most suitable for window glass, it has a high thermal expansion and poor resistance to heat. It is used for windows, some low-temperature incandescent light bulbs, tableware. Container glass is a soda-lime glass, a slight variation on flat glass, which uses more alumina and calcium, less sodium and magnesium, which are more water-soluble; this makes it less susceptible to water erosion. Sodium borosilicate glass, Pyrex: silica + boron trioxide + soda + alumina. Stan
Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate, its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y. Zircon forms in silicate melts with large proportions of high field strength incompatible elements. For example, hafnium is always present in quantities ranging from 1 to 4%; the crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, brown and green. Colorless specimens that show gem quality are a popular substitute for diamond and are known as "Matura diamond"; the name derives from the Persian zargun, meaning "gold-hued". This word is corrupted into "jargoon", a term applied to light-colored zircons; the English word "zircon" is derived from Zirkon, the German adaptation of this word. Yellow and red zircon is known as "hyacinth", from the flower hyacinthus, whose name is of Ancient Greek origin.
Zircon is ubiquitous in the crust of Earth. It occurs as a common accessory mineral in igneous rocks, in metamorphic rocks and as detrital grains in sedimentary rocks. Large zircon crystals are rare, their average size in granite rocks is about 0.1–0.3 mm, but they can grow to sizes of several centimeters in mafic pegmatites and carbonatites. Zircon is very resistant to heat and corrosion; because of their uranium and thorium content, some zircons undergo metamictization. Connected to internal radiation damage, these processes disrupt the crystal structure and explain the variable properties of zircon; as zircon becomes more and more modified by internal radiation damage, the density decreases, the crystal structure is compromised, the color changes. Zircon occurs in many colors, including reddish brown, green, blue and colorless; the color of zircons can sometimes be changed by heat treatment. Common brown zircons can be transformed into colorless and blue zircons by heating to 800 to 1000 °C. In geological settings, the development of pink and purple zircon occurs after hundreds of millions of years, if the crystal has sufficient trace elements to produce color centers.
Color in this red or pink series is annealed in geological conditions above temperatures of around 400 °C. Zircon is consumed as an opacifier, has been known to be used in the decorative ceramics industry, it is the principal precursor not only to metallic zirconium, although this application is small, but to all compounds of zirconium including zirconium dioxide, one of the most refractory materials known. Other applications include use in refractories and foundry casting and a growing array of specialty applications as zirconia and zirconium chemicals, including in nuclear fuel rods, catalytic fuel converters and in water and air purification systems. Zircon is one of the key minerals used by geologists for geochronology. Zircon is a part of the ZTR index to classify highly-weathered sediments. Zircon is a common accessory to trace mineral constituent of most felsic igneous rocks. Due to its hardness and chemical inertness, zircon persists in sedimentary deposits and is a common constituent of most sands.
Zircon is rare within mafic rocks and rare within ultramafic rocks aside from a group of ultrapotassic intrusive rocks such as kimberlites and lamprophyre, where zircon can be found as a trace mineral owing to the unusual magma genesis of these rocks. Zircon forms economic concentrations within heavy mineral sands ore deposits, within certain pegmatites, within some rare alkaline volcanic rocks, for example the Toongi Trachyte, New South Wales Australia in association with the zirconium-hafnium minerals eudialyte and armstrongite. Australia leads the world in zircon mining, producing 37% of the world total and accounting for 40% of world EDR for the mineral. South Africa is Africa’s main producer, with 30% of world production, second after Australia. Zircon has played an important role during the evolution of radiometric dating. Zircons contain trace amounts of uranium and thorium and can be dated using several modern analytical techniques; because zircons can survive geologic processes like erosion, transport high-grade metamorphism, they contain a rich and varied record of geological processes.
Zircons are dated by uranium-lead, fission-track, cathodoluminescence, U+Th/He techniques. For instance, imaging the cathodoluminescence emission from fast electrons can be used as a prescreening tool for high-resolution secondary-ion-mass spectrometry to image the zonation pattern and identify regions of interest for isotope analysis; this is done scanning electron microscope. Zircons in sedimentary rock can identify the sediment source. Zircons from Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton, Western Australia, have yielded U-Pb ages up to 4.404 billion years, interpreted to be the age of crystallization, making them the oldest minerals so far dated on Earth. In addition, the oxygen isotopic compositions of some of these zircons have been interpreted to indicate that more than 4.4 billion years ago there was water on the surface of the Earth. This interpretation is supported by additional trace element data, but is the subject of debate. In 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks in the Jack Hills of Western Australia.
According to one of the researchers, "If life arose quickly on Earth... it could be common in the universe