The results of simultaneous measurements of noctilucent clouds (NLC) position in a number of ground-based locations are presented. Observational data of 14 bright NLC events over 5 years is used for building the altitude maps of cloud fields using triangulation technique updated for multi-location case. Statistical distribution of NLC altitude and its change during the summer season is considered. Mean NLC altitudes are compared with colorimetric technique based on the same data and simple radiation transfer model. This can be used to check the model and estimate the accuracy of single-camera technique of NLC altitude measurements. Results and methods are suggested for net ground-based survey of noctilucent clouds.

Ground-based observations of the natural hydroxyl (OH) nightglow at altitudes of 85-90 km are used for deriving the rotational temperature of excited OH, which is close to the neutral atmospheric temperature. For filtering of mesoscale perturbations, we use differences between pairs of measured values of OH rotational temperature separated with fixed time intervals in the range of 0.5-2 h. The filtering is applied for studying mesoscale variations of temperature near the mesopause according to the data of spectral OH nightglow measurements at observatories of Zvenigorod (56 degrees N, 37 degrees E.) in the years 2004-2016, Tory (52 degrees N, 103 degrees E) in 2012-2017 and Maymaga (63 degrees N, 130 degrees E) in 2000-2015. Monthly-mean values and variances of temperature disturbances with periods 0.7-8.2 h are determined. Semiempirical and statistical approaches are used to estimate and subtract variances of the instrumental dark current noise and uncorrelated in time fluctuations. Seasonal and interannual variations in standard deviations of correlated in time mesoscale perturbations of the OH rotational temperature at the considered observational sites are studied. They can give information about multiyear changes in the activity of atmospheric acoustic-gravity waves propagating through the OH layer near the mesopause. (c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved.

The paper describes technical characteristics and presents the first scientific results of a novel infrared imaging system (imager) for studies of nightglow emissions coming from the hydroxyl (OH) and molecular oxygen (O2) layers in the mesopause region (80–100 km) above northern Scandinavia. The OH imager was put into operation in November 2022 at the Swedish Institute of Space Physics in Kiruna (67.86° N, 20.42° E; 400 m altitude). The OH imager records selected emission lines in the OH(3-1) band near 1500 nm to obtain intensity and temperature maps at around 87 km altitude. In addition, the OH imager registers infrared emissions coming from the O2 IR A-band airglow at 1268.7 nm in order to obtain O2 intensity maps at a slightly higher altitude, around 94 km. This technique allows the tracing of wave disturbances in both horizontal and vertical domains in the mesopause region. Validation and comparison of the OH(3-1) rotational temperature with collocated lidar and Aura Microwave Limb Sounder (MLS) satellite temperatures are performed. The first scientific results obtained from the OH imager for the first winter season (2022–2023) are discussed.

The problem of distinguishing the solar rotation from lunar tidal origin with the period of about 27 days in time series of geophysical data is considered. Although power spectra of some solar indices and of the lunar tidal gravitational potential contain coinciding or very close spectral peaks (with periods of 27.32 and 27.44 days), examination of the fine structure of the spectra for 1962-2019 allows us extracting a pair of determinative spectral peaks with the periods of 27.17 and 27.55 days indicating the solar rotation or lunar (tidal) origin of the quasi 27-day oscillation. This technique is illustrated by analyzing time series of the geomagnetic Ap index demonstrating that its 27-day oscillation is of a solar origin.

The 2020 summer season had more frequent than usual occurrences of noctilucent clouds (NLCs) in the Northern Hemisphere at middle latitudes (45-50 degrees N), with the lowest latitude at which NLCs were seen being 34.1 degrees N. In order to investigate a reason for this extraordinary NLC season, we have analyzed long-term Aura/MLS satellite data for all available summer periods from 2005 to 2021. Both Aura/MLS summer temperature and water vapor in the mesopause region, between about 79 and 89 km altitude, have been considered. There has been a decrease in the summer mesopause temperature between 2016 and 2020. At the same time, water vapor mixing ratio has significantly increased (by about 12-17%) in the zonal mean H2O value in the 2020 summer compared to 2017. There exists a positive linear trend in the H2O amount by about 5% between 2005 and 2021 at middle latitudes 45-50 degrees N at 0.0046 hPa. A combination of lower mesopause temperature and water vapor mixing ratio maximum at middle latitudes is the main reason for frequent and widespread occurrences of NLCs seen around the globe at middle latitudes in the summer of 2020. The 24th solar cycle minimum can explain neither the H2O maximum nor NLC maximum in 2020.

Abstract. The 2020 summer season has revealed frequent occurrences of noctilucent clouds (NLCs) around the Northern hemisphere at middle latitudes (45–55° N), with the lowest latitude at which NLCs were seen being 34.1° N. In order to investigate a reason for this NLC extraordinary summer season, we have analyzed long-term Aura/MLS satellite data for all available summer periods from 2005 to 2020. Both Aura/MLS summer temperature and water vapor in the upper mesosphere and the mesopause region, between 74 and 89 km altitude, have been considered. We have found that there has been a moderate decrease in the upper mesosphere temperature between 2016 and 2020 and no dramatic changes have been observed in temperature in the summer of 2020 at the middle latitude mesopause. At the same time, water vapor concentration has significantly increased (by about 12–15 %) in the zonal mean H2O value in the 2020 summer compared to 2017, meaning that the summer mesopause at middle latitudes has become more wet. At the same time, no increase in water vapor has been detected at the high latitude high altitude mesopause. A combination of lower mesopause temperature and water vapor concentration maximum at middle latitudes is the main reason for frequent and widespread occurrences of NLCs seen around the globe at middle latitudes in the summer of 2020. The 24th solar cycle minimum cannot explain the H2O maximum in 2020 since the correlation between Lyman-α flux and the amount of water vapor is low. The increase in volcanic activity from 2013 to 2015 (and its recent maximum occurred in 2015) explains the increased amount of water vapor in the upper mesosphere for the past years and its maximum in 2020 due to volcanic water vapor being injected into the atmosphere and transported into the upper mesosphere. The 5-year delay between volcanic activity and water vapor maximum is well explained by a general meridional-vertical atmospheric circulation.

According to the ground-based spectral observations of airglow emissions in the near infrared at Zvenigorod in 2000-2019, multi-year changes in the intensity of O(2)A(0-1) band at 865 nm and OH(6-2) band at 840 nm are studied. It was shown that the intensities of both the emissions had a significant negative long-term time trend and a positive response to the change of solar activity in the 11-year cycle. In the spectrum of their interannual harmonic variations, statistically significant quasi-decade and quasi-two-decade oscillations were found.

Digital difference filters were used for the analysis of data of the spectral observations of the rotational temperature and emission intensity of vibrationally excited hydroxyl (OH*) at altitudes 85-90 km at observatories Zvenigorod (56 degrees N, 37 degrees E) for 2004-2016 years and Tory (52 degrees N, 103 degrees E) for 2012-2017. The monthly-average values and standard deviations of mesoscale perturbations of the OH* emission characteristics with periods 0.8-11 h are obtained. These mesoscale perturbations may reflect internal gravity waves (IGWs) in the mesopause region. To filter out mesoscale perturbations, differences between the sequential values of the OH* emission characteristics, averaged over the intervals by duration from 0.5 h to 2 h, were obtained. The average monthly variances of mesoscale perturbations in the OH* rotational temperature obtained at Tory are larger compared to Zvenigorod ones. Average seasonal changes of relative mesoscale variances demonstrate maxima in winter and in summer, with the summer maximum shifted closer to spring months for the Tory station. The reasons for the differences could be different orography and jet streams in the lower and middle atmosphere, also different spectra of IGW horizontal wavelengths due to different geometry of observations at Tory and Zvenigorod.

Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Journal of Geophysical Research - Atmospheres. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing the latest version by default [v1]The first quantitative estimation of the influence of volcanic activity on noctilucent cloudsAuthors Peter A. Dalin iD Nikolay Pertsev iD Vladimir Perminov iD Vitaly Romejko See all authors Peter A. DaliniDCorresponding Author• Submitting AuthorSwedish Institute of Space PhysicsiDhttps://orcid.org/0000-0002-1815-7773view email addressThe email was not providedcopy email addressNikolay PertseviDA. M. Obukhov Institute of Atmospheric Physics, RASiDhttps://orcid.org/0000-0002-8900-5494view email addressThe email was not providedcopy email addressVladimir PerminoviDA. M. Obukhov Institute of Atmospheric Physics, RASiDhttps://orcid.org/0000-0002-2293-1442view email addressThe email was not providedcopy email addressVitaly RomejkoThe Moscow Association for NLC Researchview email addressThe email was not providedcopy email address

We formulate a novel mathematical model to describe the development of acute HIV-1 infection and the antiviral immune response. The model is formulated using a system of delay differential- and integral equations. The model is applied to study the possibility of eradication of HIV infection during the primary acute phase of the disease. To this end a combination of analytical examination and computational treatment is used. The model belongs to the Wazewski differential equation systems with delay. The conditions of asymptotic stability of a trivial steady state solution are expressed in terms of the algebraic Sevastyanov-Kotelyanskii criterion. The results of the computational experiments with the model calibrated according to the available estimates of parameters suggest that a complete elimination of HIV-1 infection after acute phase of infection is feasible.

Simple digital filtering is used for studying mesoscale variations of the rotational temperature of excited hydroxyl (OH*) at heights 85 – 90 km according to the data of spectral measurements at observatories Zvenigorod (56°N, 37°E.) in years 2004 – 2016, Tory (52°N, 103°E) in 2012 – 2017 and Maymaga (63°N, 130°E) in 2000 - 2015. Monthly-mean values and standard deviations of OH* temperature disturbances with periods 0.7 – 8 hr are determined, which may reflect the intensity of internal gravity waves in the mesopause region. The filtering of mesoscale variations was performed by calculating the differences between the measured values of OH* temperature separated with time intervals of 0.5 - 2 hr. Seasonal and interannual changes in the mesoscale variances of the temperature at the observational sites are studied.

The new mineral chlorkyuygenite, Ca12Al14O32[(H2O)(4)Cl-2] (I (4) over bar 3d, a=12.0285(1)angstrom, V=1740.34(3)angstrom(3)), was discovered as an accessory mineral in Ca-humite zones of calcareous skarn xenoliths in ignimbrites of the Upper Chegem Caldera, Northern Caucasus, Kabardino-Balkaria, Russia. Rounded grains and crystals with tris-tetrahedral form of chlorkyuygenite up to 50 mu m and aggregates up to 100-150 mu m in size are enclosed in chegemite, reinhardbraunsite and srebrodolskite. Chlorkyuygenite also forms rims on wadalite crystals. Chegemite-fluorchegemite, reinhardbraunsite-kumtyubeite, rondorfite, hydroxylellestadite, lakargiite, perovskite, kerimasite, elbrusite, ettringite-group minerals, hydrocalumite, bultfonteinite, and minerals of the katoite-grossular series are associated with chlorkyuygenite. Larnite, spurrite and galuskinite are noted as relics in Ca-humites. Chlorkyuygenite is colourless, occasionally with a greenish or yellowish tint, and the streak is white. The mineral is transparent with strong vitreous lustre, it is isotropic, n=1.672(1) (589 nm). The microhardness VHN load 50 g is 632(37) kg mm(-2), corresponding to 5-51/2 hardness according to the Mohs scale; the calculated density is 2.941 g cm(-3). The calculated Gladstone-Dale's compatibility factor 1-(K-p/K-c) = -0.016 is superior. The holotype specimen of chlorkyuygenite from the chegemite zone is characterized by relatively constant composition corresponding to the crystal-chemical formula Ca-11.979(Al12.986Fe0.8233+Si0.179Ti0.0334+)(Sigma 14.021)O-32 [(H2O)(3.767) Cl-2.234](Sigma 6). In the Raman spectra of chlorkyuygenite the following characteristic main bands are distinguished: 202, 321, 511, 705, 776 and 881 cm(-1). A broad band with two maxima near 3400 and 3200 cm(-1) is observed in the OH region and it is related to H2O in the structural cages of chlorkyuygenite. The molecular water is completely released from the mineral structure at about 550 degrees C. Chlorkyuygenite crystallized initially as chlormayenite, which later was altered under influence of volcanic gases containing water vapour.

Eltyubyuite (IMA2011-022), ideally Ca12Fe103+Si4O32Cl6 i.e. the Fe3+ analogue of wadalite, Ca12Al10Si4O32Cl6, was discovered in altered silicate-carbonate xenoliths in the diatreme fades of ignimbrites in the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia. Eltyubyuite forms light-brown or yellow crystals with tetrahedral habit up to 10 pm across in rondorfite or larnite grains and commonly overgrows wadalite. Associated minerals are hydroxylellestadite, edgrewite-hydroxyled-grewite, chegemite-fluorchegemite, cuspidine, lakargiite, perovskite, kerimasite, srebrodolskite and dovyrenite. Eltyubyuite formed by contact metamorphism of calcareous sediments under sanidinite-facies conditions (T > 800 degrees C, P <1-2 kbar). Electron microprobe analysis (mean of 9 points) gave in weight% (s.d.): SiO2 9.57(0.32), TiO2 0.48(0.27), Al2O3 3.45(1.81), MgO 0.08(0.07), CaO 36.84(0.91), Fe2O3, Cl 9.60(0.48); O = Cl -2.13, Sum 98.26, and an empirical formula based on 26 cations, Ca12.12Mg0.04Ti0.11Fe9.41Al1.26Si2.98O31.89Cl5.04, which simplifies to Ca-12(Fe3+,Al)(11)Si3O32Cl5. Electron-back-scattered diffraction yields isometric symmetry, space group I<(4)over bar>3d (no. 220), a = 12.20(3) angstrom, V = 1815.85(9) angstrom(3), Z = 2. Calculated density and refractive index are 3.349 g/cm(3) and 1.85, respectively. The main bands in Raman spectra of eltyubyuite are attributed to [Fe3+O4](5-): 700-710 cm(-1) (stretching vibrations), 460-470 cm(-1) (bending vibrations), whereas bands <400 cm(-1) are assigned to Ca-O and Ca[Fe3+O4](5-) vibrations. The mineral is named for the Balkarian village Eltyubyu, which is situated near the type locality. Eltyubyuite has subsequently been found in altered xenoliths within volcanic rocks of Eifel, Germany and Kel' Highland (volcano Shadil-Khokh), Southern Ossetia.

Dzhuluite, Ca3SbSnFe33+O12 (Ia (3) over bard, a = 12.536(3) angstrom, v = 1970.05(9) angstrom(3), Z = 8), a new antimony garnet of the bitildeite-group, was discovered in a kumtyubeite zone in close proximity to the contact with unaltered ignimbrite in a skarn xenolith from the Upper Chegem Caldera, Northern Caucasus, Russia. The empirical formula of the holotype dzhuluite is (Ca2.954Fe0.0432+Mg0.003)(Sigma 3.000) (Sn0.850Sb0.7645+Zr0.121U0.1276+Ti0.0704+Sc0.009Nb0.0585+Hf0.001)(Sigma 2.001)(Fe2.0513+Al0.653Fe0.1822+ Ti0.0874+Si0.028)Sigma O-3.001(12). Associated minerals are kumtyubeite, cuspidine, fluorchegemite, larnite, fluorite, wadalite, rondorfite, hydroxylellestadite, perovskite, lakargiite, kerimasite, elbrusite, srebrodolskite, bultfonteinite, ettringite group minerals, hillebrandite, afwillite, tobermorite-like minerals, hydrocalumite and hydrogrossular. Dzhuluite forms poikilitic crystals < 50 mu m in size that are light-yellow to dark-brown and with a creamy streak. The lustre is strongly vitreous. The calculated density of dzhuluite ranges from 4.708 to 4.750 g/cm(3). Raman spectra are analogous to those of kimzeyite, kerimasite and other bitildeite-group minerals. Dzhuluite formed at high temperature during a retrograde stage of primary rock alteration in the larnite subfacies (sanidinite facies) as a result of fluorine metasomatism.

Members of the edgrewite Ca-9(SiO4)(4)F-2-hydroxyledgrewite Ca-9(SiO4)(4)(OH)(2) series, structural analogues of clinohumite-hydroxylclinohumite series, Mg-9(SiO4)(4)(F,OH)(2), were discovered in xenoliths of carbonate-silicate rock altered to skarn within ignimbrites of the Upper Chegem volcanic structure, Kabardino-Balkaria, Northern Caucasus, Russia. The new minerals occur sparingly in zones containing bultfonteinite, hillebrandite, jennite, and chegemite, as well as rare relics of larnite and rondorfite enclosed in a matrix of hydroxylellestadite. Edgrewite and hydroxyledgrewite are largely altered to jennite in places with admixed zeophyllite and trabzonite, and are preserved as elongate relics mostly 0.1-0.4 mm long in the central part of atoll-like pseudomorphs. The new minerals form a solid-solution series Ca-9(SiO4)(4)(F,OH)(2), in which the content of the edgrewite end-member Ca-9(SiO4)(4)F-2 ranges from 74% (F = 3.64 wt%) to 31% (F = 1.52 wt%).Structure refinement of crystals containing 51% and 37% of the edgrewite end-member gave, respectively, R-1 = 3.03%, space group P2(1)/b11 (no. 14), Z= 2, a = 5.06870(10), b= 11.35790(10), c= 15.4004(2) angstrom, alpha = 100.5980(10)degrees, V= 871.47(3) angstrom(3); and R-1 = 1.61%, space group P2(1)/b11 (no. 14), Z = 2, a = 5.06720(10), b= 11.35450(10), c = 15.3941(2) angstrom, a = 100.5870(10)degrees, and V= 870.63(2) angstrom(3).Minerals of the edgrewite-hydroxyledgrewite series are colorless, optically biaxial (+), 2V(meas) = 80(5)degrees; 2 V-calc = 78.7 degrees; dispersion r > v, medium; orientation: Z = a, X (boolean AND) c = 12(2)degrees; edgrewite: alpha = 1.621(2), beta = 1.625(2), gamma = 1.631(2); hydroxyledgrewite: alpha = 1.625(2), beta = 1.629(2), gamma = 1.635(2) (589 nm). The micro-hardness VHN50= 352-366 kg/mm(2) corresponds to the Mohs scale of 5.5-6. 5. FTIR spectra of edgrewite and hydroxyledgrewite show resolved bands at (edgrewite/hydroxyledgrewite, cm(-1)): 3558 and 3551 and 3543/3554, absent/3486, 1075/1075, 996/996, 980/982, 934/933, 917/918, 904/903, 890/884, 864/864, 842/842, 818/820. Raman spectra are characterized by the following bands (edgrewite/hydroxyledgrewite, cm(-1)) at: 921/923, 889/890, 839/840, and 815/814 (SiO4 stretching), at: 556/559, 527/527, 423/419,406/404, and 394/394 (SiO4 bending), 309/295, 269/256, and 163/166 (CaO6). In the OH stretching region three bands are noted at 3554, 3547, and 3540 cm(-1) for edgrewite and two -3550 and 3475 cm(-1) for hydroxyledgrewite confirming the corresponding IR spectra. The major difference in Raman and IR spectra of edgrewite and hydroxyledgrewite is the presence of two resolved peaks in the OH stretching region at ca. 3550 and 3480 cm(-1) for hydroxyledgrewite.

The new mineral pavlovskyite Ca-8(SiO4)(2)(Si3O10) forms rims together with dellaite Ca-6(Si2O7)(SiO4) (OH)(2) around galuskinite Ca-7(SiO4)(3)CO3 veins cutting calcio-olivine skarns in the Birkhin gabbro massif. In addition, skeletal pavlovskyite occurs in cuspidine zones of altered carbonate xenoliths in the ignimbrites of the Upper Chegem caldera (North Caucasus). The synthetic analog of pavlovskyite has been synthesized before and is known from cement-like materials. Isotypic to pavlovskyite is the synthetic germanate analog Ca-8(GeO4)(2)(Ge3O10). The crystal structure of pavlovskyite, space group Pbcn, a = 5.0851(1), b = 11.4165(3), c = 28.6408(8) angstrom, V = 1662.71(7) angstrom(3), Z= 4, has been relined from X-ray single-crystal data to R1 = 3.87%. The new colorless mineral has a Mohs hardness of 6-6.5, biaxial (-), alpha = 1.656(2), beta = 1.658(2), gamma = 1.660(2) (589 nm), 2V (meas) = 80(5)degrees, 2V (calc) = 89.9 degrees, medium dispersion: r > v, optical orientation: X = b, V = e, Z = a.For comparison with pavlovskyite, the crystal structure of kilchoanite Ca-6(SiO4)(Si3O10) from the Birkhin massif [space group I2cm, a = 11.4525(2), b = 5.0867(1), c = 21.996(3) angstrom, V = 1281.40(4) angstrom(3), Z = 4] has been refined from single-crystal X-ray data to R1 = 2.00%.Pavlovskyite represents a 1:1 member of a polysomatic series with calcio-olivine gamma-Ca2SiO4 and kilchoanite C-4(SiO4)(Si3O10) as end-member modules. The structure is characterized by strongly folded trisilicate units (Si3O10) interwoven with a framework of CaO6 and CaO8 polyhedra. Olivine-like slices with orthosilicate groups are interstratified with the characteristic trisilicate module of' Ca-4(Si3O10) composition. Although the optical properties of pavlovskyite and kilchoanite are similar, both minerals can be distinguished by chemical analyses (different Ca/Si ratio), X-ray diffraction, and Raman spectroscopy. The new mineral is named after V.E. Pavlovsky (1901-1982), an outstanding geologist in the area of Eastern Siberia, in particular of the Baikal region.

Sessions C576hierarchical level is formed.In the same way the cluster of the 2 nd level is formed, etc.Thus, we interpreter the formation of silica spheres as the process of hierarchical self-organization of matter at nanolevel.This work is

The new mineral vorlanite, (CaU6+)O-4, D-calc = 7.29 g/cm(3), H = 4-5, VHN10= 360 kg/mm(2), was found near the top of Mt. Vorlan in a calcareous skarn xenolith in ignimbrite of the Upper Chegem caldera in the Northern Caucasus, Kabardino-Balkaria, Russia. Vorlanite occurs as aggregates of black platy crystals up to 0.3 mm long with external symmetry m. The strongest powder diffraction lines are [d(angstrom)1(hkl)]: 3.107/(111), 2.691/(200), 1.903/(220), 1.623/(311), 1.235/(331), 1.203/(420), 1.098/(422), 0.9101(531). Single-crystal X-ray study gives isometric symmetry, space group Fm (3) over barm, a= 5.3813(2) angstrom, V= 155.834(10) angstrom(3), and Z= 2. X-ray photoelectron spectroscopy indicate that all U in vorlanite is hexavalent. The mineral is isostructural with fluorite and uraninite (U4+O2). In contrast to synthetic rhombohedral CaUO4, and most U6+ minerals, the U6+ cations in vorlanite are present as disordered uranyl ions. Ca-[8](2+) and U-[8](6+) are disordered over a single site with average M-O = 2.33 angstrom.Vorlanite is believed to be a pseudomorphic replacement of originally rhombohedral CaUO4. We assume that this rhombohedral phase transformed by radiation damage to cubic CaUO4 (vorlanite). The new mineral is associated with larnite, chegemite, reinhardbraunsite, lakargiite, rondorfite, and wadalite, which are indicative of high-temperature formation (>800 degrees C) at shallow depth.

Rusinovite, Ca 10 (Si 2 O 7 ) 3 Cl 2 , was discovered in an altered carbonate-silicate xenolith enclosed in ignimbrites of the Upper Chegem volcanic caldera. The mineral is named after Vladimir Leonidovich Rusinov (1935–2007), a Russian petrologist and expert in the field of thermodynamics of non-equilibrium mineral systems. A synthetic analogue of rusinovite is also known. The new mineral has an OD structure of which only the average structure could be determined based on strong and sharp reflections recorded by single-crystal X-ray diffraction: space group Cmcm , a = 3.7617(2), b = 16.9385(8), c = 17.3196(9) A, V = 1103.56(10) A 3 , Z = 2. The average structure ( R 1 = 3.18 %) is characterized by columns of face-sharing disilicate units extending parallel to a . However, in the true structure only each second (Si 2 O 7 ) unit is occupied. Although rusinovite has a stoichiometry similar to the apatite-group mineral nasonite, Pb 6 Ca 4 (Si 2 O 7 ) 3 Cl 2 , the two structures are considerably different. Rusinovite has following optical properties: α = 1.645(2), β = 1.664(2), γ = 1.675(3); Δ = 0.030, 2V meas = −75(10) °; 2V calc = −74.6 °; the Mohs hardness is 4–5, the density is 2.91 g/cm 3 . The mineral forms fibrous crystals often intergrown into spherolites and displays good cleavage parallel to (010). The Raman spectrum of rusinovite strongly resembles that of another skarn calcium-disilicate: rankinite, Ca 3 Si 2 O 7 .