Naturally-occurring Minerals Research Articles

Modulator-Free Green Synthesis of the Calcium-Terephthalate Metal-Organic Framework Derived from Waste Eggshells

Conventionally, the four-component calcium-terephthalate (Ca-BDC) metal–organic framework (MOF), Ca(BDC)(DMF)(H2O), has been synthesized from commercial calcium nitrate (Ca(NO3)2) and calcium carbonate (CaCO3), which in turn are manufactured from naturally-occurring minerals by energy-intensive processes. This study presents a primary investigation on the modulator-free solvothermal synthesis of Ca(BDC)(DMF)(H2O) derived from waste eggshells as green precursors. Ca(BDC)(DMF)(H2O) crystallizes as two possible phases, namely the triclinic (Ca-BDC-tric) and orthorhombic (Ca-BDC-orth) phase. This study presents an in-depth investigation on the influence of reaction temperature and solvent volumes on eggshell-derived Ca(BDC)(DMF)(H2O) product phase. Investigations were conducted at long reaction times to ensure complete reaction of green eggshell precursors. Low water (H2O) and high N,N-dimethylformamide (DMF) volumes were found to inhibit solvothermal synthesis. 7.6 mL H2O was determined to be the minimum H2O volume threshold for successful Ca-BDC-tric synthesis, above which further increasing the H2O volume produced porous Ca-BDC-tric at higher yield, which proved favorable due to reduction of toxic DMF. Ca-BDC-orth and Ca-BDC-tric were obtained at 150 °C and 110 °C respectively, whereas dual-formation of both phases prevailed at 130 °C, thereby informing the rough temperature range at which Ca-BDC-tric morphs into Ca-BDC-orth. Ultimately, this study introduces a green solvothermal method for valorizing eggshell waste into value-added Ca(BDC)(DMF)(H2O) for sustainable eggshell waste management and alleviation of environmental health concerns associated with eggshell disposal.

Identifying the source of groundwater contaminants in West-Central Wisconsin, U.S.A.: Geochemical and mineralogical characterization of the Cambrian sandstone aquifer

Naturally-sourced groundwater quality issues are common, but there is rarely a geochemical and mineralogical dataset of aquifer properties for comparison. This study utilizes geochemical and mineralogical data to characterize naturally-occurring minerals that are potential groundwater contaminants in the Cambrian Eau Claire – Mount Simon aquitard-aquifer system of west-central Wisconsin, U.S.A. A high-resolution portable x-ray fluorescence elemental analysis was used for initial characterization of geochemistry and chemostratigraphy of well cutting and drill core samples. Then, a subset of sample materials was analyzed mineralogically and geochemically using XRD and ICP-MS, respectively. Elevated concentrations of arsenic, phosphorous, strontium, and various metals within the aquitard-aquifer sandstone were identified, mostly associated with sulfide minerals and iron (hydr)oxides and suggestive of Mississippi Valley-type mineralization. Similar elemental contaminants in surface and groundwater in the study area indicate that the observed trace element-bearing minerals are a natural source of groundwater contamination, most likely through release into groundwater during fluctuating redox and pH conditions near the water table. Co-occurrence of iron (hydr)oxide-coated sulfide minerals near the water table, and observations of sulfide oxidation post-drilling, suggests sulfides in these units are actively oxidizing. Well construction recommendations based on these results should mitigate current or future pumping of trace element-contaminated groundwater and in the vast majority of cases eliminate naturally-occurring contaminants as a potential source. This study provides an extensive baseline dataset of aquifer mineralogy and trace element composition (and an efficient approach for data collection) that is necessary for interpreting and attributing possible future groundwater quality issues.

Influence of wollastonite - GGBS on properties of ternary blended self compacting concrete

In an innovative world self compacting concrete exhibiting significant role over conventional concrete with its excellent functionalities with capability to stretch to all corners under its own mass which empowers reliable quality with an astonishing finish. In order to produce such a durable concrete materials namely admixtures were added, these materials not only helps reducing the expenditure of cement but also exhibit their salient impact on properties of concrete. Wollastonite being a multi-functional material is a natural occurring mineral shaped as an output of interactivity between limestone and silica in hot magma. This paper reports on infliction of both wollastonite and GGBS as partial replacement to cement by mass for M30 grade of self compacting concrete with up to 0–25% with an interval of 5% where as GGBS content 20% kept constant thorough out the study, several tests were executed on both freshly mixed state to get SCC workability parameters, and in dry state to get desired outcome on account of mechanical properties trails were directed under characteristics of strength are compression, flexure and spilt tensile, acid attack and sorptivity assessments were guided on a perspective to get durable aspects. Experimental findings were indicated that substitution level of wollastonite up to 15% when blended with 20% GGBS content shown superiority in results.

Leaching Kinetics of Valuable Metals

Leaching is a primary extractive operation in hydrometallurgical processing, by which a metal of interest is transferred from naturally-occurring minerals into an aqueous solution [...]

Prevention of Ladle Furnace Slag Disintegration Through Different Slag Additives

Ladle refining is a popular secondary metallurgy process and plays a vital role in achieving the desired chemistry and temperature during steelmaking. The slag produced after ladle refining mostly contains dicalcium silicate (C2S). The presence of high C2S in slag leads to the disintegration of slag into fine powder during cooling due to phase transformation of C2S. The adverse impact is that the dust is easily aerated and carried by wind creating environmental pollution and makes the working area unsafe. In this paper, an attempt was made to study the effect of the addition of different additives on the disintegration of slag. Initial laboratory experiments were conducted with different additives such as Colemanite (boron-based mineral), silica-rich synthetic slag, and a siliceous natural occurring mineral perlite. Analysis of slag samples was carried out before and after treatment with additives. Based on the optimized conditions, industrial trials were conducted with different additives, and its success was measured in terms of lumpy slag formation. It was successfully studied that the addition of 10% of perlite during ladle furnace treatment process helped in preventing the slag disintegration by 90%.

Mineral control of organic carbon storage in acid temperate forest soils in the Basque Country

Soil minerals are known to play a major role in soil organic carbon (SOC) stabilization. However, the exact nature of the role is still poorly understood as comparative studies are complicated by the fact that mineralogy usually varies with other important factors such as climate, land-use, texture and acidity. This study investigated naturally-occurring minerals and C storage in nine mature, second-rotation Pinus radiata D. Don forest plantations at a similar development stage and growing under similar climatic conditions, but established on soils derived from three different parent materials: sandstone, basalt and trachyte. We quantified the SOC stocks in the 0–20 cm soil layer, clay-size minerals and metal oxides. The distribution of SOC in labile and mineral-bound fractions and the chemical structure of the SOC were also determined, by CPMAS NMR spectroscopy. For similar tree biomass, mean SOC storage was 2 times higher in the soils derived from basalt and 2.5 times higher in the soils derived from trachyte which were relatively rich in chlorite/vermiculite mixed layers and short-range order aluminium and iron forms, than in the sandstone-derived soils dominated by illite and with no short-range order aluminium. The parent material also affected the major C components of the SOC. Thus, the proportion of aromatic-C forms in the total SOC was higher in the sandstone-derived soil than in the soils of volcanic origin. Furthermore, the proportion of SOC in the mineral-bound fraction was around 30% in the sandstone-derived soil and around 50% in the volcanic soils. We conclude that estimates of ecosystem SOC stocks in acid temperate forest soils should include proxies for clay mineralogy, such as phyllosilicate minerals, contents of Fe and Al (hydr-) oxides and non-crystalline compounds. In addition, we recommend the inclusion of soil parent material as a proxy in models aimed at estimating regional SOC stocks.

Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions.

Combined size and density fractionation (CSDF) is a method used to physically separate soil into fractions differing in particle size and mineralogy. CSDF relies on sequential density separation and sedimentation steps to isolate (1) the free light fraction (uncomplexed organic matter), (2) the occluded light fraction (uncomplexed organic matter trapped in soil aggregates) and (3) a variable number of heavy fractions (soil minerals and their associated organic matter) differing in composition. Provided that the parameters of the CSDF (dispersion energy, density cut-offs, sedimentation time) are properly selected, the method yields heavy fractions of relatively homogeneous mineral composition. Each of these fractions is expected to have a different complexing ability towards organic matter, rendering this a useful method to isolate and study the nature of organo-mineral interactions. Combining density and particle size separation brings an improved resolution compared to simple size or density fractionation methods, allowing the separation of heavy components according to both mineralogy and size (related to surface area) criteria. As is the case for all physical fractionation methods, it may be considered as less disruptive or aggressive than chemically-based extraction methods. However, CSDF is a time-consuming method and furthermore, the quantity of material obtained in some fractions can be limiting for subsequent analysis. Following CSDF, the fractions may be analyzed for mineralogical composition, soil organic carbon concentration and organic matter chemistry. The method provides quantitative information about organic carbon distribution within a soil sample and brings light to the sorptive capacity of the different, naturally-occurring mineral phases, thus providing mechanistic information about the preferential nature of organo-mineral interactions in soils (i.e., which minerals, what type of organic matter).

Terra verde: Overcoming the problem of transparency by crystal engineering

Abstract Terra verde, or Green Earth, a naturally-occurring mineral and green pigment consisting of celadonite or glauconite, is one of the most commonly-used pigments in works of art and their conservation. Its widespread use is owed primarily to its insensitivity to light, its neutral pH, and its high stability in air and moisture – attributes that collectively make it virtually unreactive with other components in an artefact. Notwithstanding this, the use of terra verde in the conservation of objects of cultural heritage is hindered due to its minimal tinting strength and hiding power, which makes the pigment effectively transparent when applied on the canvas with the most common binding media. This gives rise to problems in retouching during the restoration process. We report a robust and reliable method to overcome the problem of transparency through the application of crystal engineering techniques on the pigment Verona Green Earth, or Verona Terra Verde (VTV). The purchased pigment was co-crystallised with a selection of different co-formers and analysis was carried out on both starting compound and product via IR and XRF spectroscopy, hot-stage microscopy and powder X-ray diffraction. The results of the experiments conducted show an increase in the pigment's opacity without affecting its colour intensity.

Ceramics in dentistry

Ceramics for dental restorations have evolved from fragile materials made from naturally-occurring minerals to high-strength synthetic ceramics of today. Manufacturing techniques have moved from purely manual processing to computer assisted design and manufacture (CAD/CAM). The development has been rapid during the last 20 years and is still ongoing regarding the balance of esthetics and strength, and cementation procedures.

Role of Mineral Surfaces in Prebiotic Chemical Evolution. In Silico Quantum Mechanical Studies.

There is a consensus that the interaction of organic molecules with the surfaces of naturally-occurring minerals might have played a crucial role in chemical evolution and complexification in a prebiotic era. The hurdle of an overly diluted primordial soup occurring in the free ocean may have been overcome by the adsorption and concentration of relevant molecules on the surface of abundant minerals at the sea shore. Specific organic–mineral interactions could, at the same time, organize adsorbed molecules in well-defined orientations and activate them toward chemical reactions, bringing to an increase in chemical complexity. As experimental approaches cannot easily provide details at atomic resolution, the role of in silico computer simulations may fill that gap by providing structures and reactive energy profiles at the organic–mineral interface regions. Accordingly, numerous computational studies devoted to prebiotic chemical evolution induced by organic–mineral interactions have been proposed. The present article aims at reviewing recent in silico works, mainly focusing on prebiotic processes occurring on the mineral surfaces of clays, iron sulfides, titanium dioxide, and silica and silicates simulated through quantum mechanical methods based on the density functional theory (DFT). The DFT is the most accurate way in which chemists may address the behavior of the molecular world through large models mimicking chemical complexity. A perspective on possible future scenarios of research using in silico techniques is finally proposed.

The Microstructural Investigation of Vermiculite-Infiltrated Electron Beam Physical Vapor Deposition Thermal Barrier Coatings

Abstract Thermal barrier coatings (TBCs) are widely used in aerospace and aviation industries for materials required to withstand severe environments such as oxidation, hot-corrosion failure and CMAS (calcia–magnesia–alumina–silica) attack or vermiculite corrosion. This is particularly apparent in vermiculite, which can penetrate sand, volcanic ash and is the most destructive damage mechanism in the TBC system. Impurities from the desert environment such as calcia–magnesia–alumina–silica (CMAS) cause degradation of TBCs. In this research, CoNiCrAlY metallic bond coatings were deposited on Inconel 718 nickel based superalloy substrates with a thickness of around 100 μm using a Cold Gas Dynamic Spray (CGDS) technique. Production of TBCs were carried out with deposition of YSZ ceramic top coating material using Electron Beam Physical Vapor Deposition (EB-PVD), with a thickness of around 200 μm. The effect of CMAS with spreading naturally-occurring mineral (vermiculite) on TBC samples were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) analysis and X-ray diffraction (XRD). The microstructure evolution of YSZ and failure mechanism of TBC were evaluated.

Nomenclature of the perovskite supergroup: A hierarchical system of classification based on crystal structure and composition

AbstractOn the basis of extensive studies of synthetic perovskite-structured compounds it is possible to derive a hierarchy of hettotype structures which are derivatives of the arisotypic cubic perovskite structure (ABX3), exemplified by SrTiO3(tausonite) or KMgF3(parascandolaite) by: (1) tilting and distortion of theBX6octahedra; (2) ordering ofA- andB-site cations; (3) formation ofA-,B- orX-site vacancies. This hierarchical scheme can be applied to some naturally-occurring oxides, fluorides,hydroxides, chlorides, arsenides, intermetallic compounds and silicates which adopt such derivative crystal structures. Application of this hierarchical scheme to naturally-occurring minerals results in the recognition of a perovskite supergroup which is divided into stoichiometric and non-stoichiometricperovskite groups, with both groups further divided into singleABX3or doubleA2BB'X6perovskites. Subgroups, and potential subgroups, of stoichiometric perovskites include: (1) silicate single perovskites of the bridgmanite subgroup;(2) oxide single perovskites of the perovskite subgroup (tausonite, perovskite, loparite, lueshite, isolueshite, lakargiite, megawite); (3) oxide single perovskites of the macedonite subgroup which exhibit second order Jahn-Teller distortions (macedonite, barioperovskite); (4) fluoride singleperovskites of the neighborite subgroup (neighborite, parascandolaite); (5) chloride single perovskites of the chlorocalcite subgroup; (6)B-site cation ordered double fluoride perovskites of the cryolite subgroup (cryolite, elpasolite, simmonsite); (7)B-site cation orderedoxide double perovskites of the vapnikite subgroup [vapnikite, (?) latrappite]. Non-stoichiometric perovskites include: (1)A-site vacant double hydroxides, or hydroxide perovskites, belonging to the söhngeite, schoenfliesite and stottite subgroups; (2) Anion-deficient perovskitesof the brownmillerite subgroup (srebrodolskite, shulamitite); (3)A-site vacant quadruple perovskites (skutterudite subgroup); (4)B-site vacant single perovskites of the oskarssonite subgroup [oskarssonite]; (5)B-site vacant inverse single perovskites of the coheniteand auricupride subgroups; (6)B-site vacant double perovskites of the diaboleite subgroup; (7) anion-deficient partly-inverseB-site quadruple perovskites of the hematophanite subgroup.

Naturally-occurring iron minerals as inexpensive catalysts for CWPO

This work explores the potential application of naturally-occurring minerals as inexpensive catalysts in heterogeneous Fenton, namely catalytic wet peroxide oxidation (CWPO). The availability, low cost and environmentally friendly character of those materials make them interesting candidates for such application. The performance of magnetite, hematite and ilmenite as CWPO catalysts has been tested under different working conditions, which include temperature (25–90°C), H2O2 dose (250–1000mgL−1) and catalyst concentration (1–4gL−1). The operating temperature plays a key role on the rate of H2O2 decomposition so that with magnetite H2O2 conversion after 4h increased from 8 to 99% by increasing the temperature from 25 to 90°C. Based on the reaction mechanism proposed, a kinetic model was developed which successfully described the experimental results on H2O2 decomposition. The catalytic performance of the minerals tested at temperatures above the ambient was demonstrated using phenol (100mgL−1) as target pollutant. Unprecedented efficiencies of H2O2 consumption, higher than 80% were achieved, allowing high oxidation and mineralization, i.e. complete phenol conversion and almost 80% TOC reduction at 75°C with a catalyst loading of 2gL−1 and the theoretical stoichiometric amount of H2O2 for complete mineralization of phenol (500mgL−1). Magnetite is particularly attractive, since it showed the highest activity and can be easily separated from the liquid phase given its magnetic properties. All the minerals tested suffered low iron leaching and magnetite and hematite showed a good reusability upon three consecutive runs. However, in this case long-term durability is not a crucial issue, given the availability and low cost of these minerals.

Lithium Aluminosilicate Residue as Raw Material in the Production of Sustainable Concrete Masonry Units: A Brazilian Case

Spodumene (LiAlSi2O6) is a natural occurring mineral which is processed to produce lithium carbonate (LiCO3) and lithium hydroxide (LiOH), both used for several industrial and medical applications. The processing of spodumede generates a lithium aluminosilicate residue with no commercial value in Brazil, which is therefore landfilled. This paper studied the effect of the partial replacement of Portland cement (PC) in the production of sustainable concrete masonry units (CMU) for construction. The residue was thoroughly characterized and its interaction with PC was also assessed. Several mixes of CMU were manufactured and compared with a reference mix (without residue). Results indicated that the lithium aluminosilicate is highly reactive and may replace PC in the concrete formulations.

Enhanced autotrophic growth of Nannochloris sp. with trona buffer for sustainable carbon recycle

In this study, a potential applicability of a modified Shuisheng-4 culture medium with trona buffer for CO2(g) capture and the resultant CO2-rich solution was investigated for the autotrophic growth of Nannochloris sp. Trona is an inexpensive naturally-occurring mineral with high solubility in water. Trona solution after absorbing CO2(g) controlled at pH ~7 ~ 8 contains high dissolved inorganic carbon (DIC) concentration in water applicable to both open and closed systems and the pH is suitable for the growth. High DIC concentration was also found to enhance the autotrophic growth rate when the Na+ concentration is ~ < 0.12 M. However, the tolerance of a marine green alga, Nannochloris sp., to Na+ ion was found to twice as much as that of a freshwater green alga, Chlorella vulgaris. Therefore, it is anticipated that trona buffer solution has potential for better CO2 utilization for the mutual benefit of microalgae-derived biofuels production and carbon recycle.

Application of sorbers to mitigate greenhouse gas emissions from land-applied pig litter

Nitrous oxide is the foremost greenhouse gas (GHG)generated by land-applied manures and chemical fertilisers (Australian Government 2013). This research project was part of the National Agricultural Manure Management Program and investigated the potential for sorbers (i.e. specific naturally-occurring minerals) to decrease GHG emissions from spent piggery litter (as well as other manures)applied to soils. The sorbers investigated in this research were vermiculite and bentonite. Both are clays with high cation exchange capacities, of approximately 100–150 cmol/kg Faure 1998). The hypothesis tested in this study was that the sorbers bind ammonium in soil solution thereby suppressing ammonia (NH3)volatilisation and in doing so, slowing the kinetics of nitrate formation and associated nitrous oxide (N2O) emissions. A series of laboratory, glasshouse and field experiments were conducted to assess the sorbers’ effectiveness. The laboratory experiments comprised 64 vessels containing manure and sorber/manure ratios ranging from 1 : 10 to 1 : 1 incorporated into a sandy Sodosol via mixing. The glasshouse trial involved 240 pots comprising manure/sorber incubations placed 5 cm below the soil surface, two soil types (sandy Sodosol and Ferrosol) and two different nitrogen (N) application rates (50 kg N/ha and 150 kg N/ha) with a model plant (kikuyu grass). The field trial consisted of 96, 2 m · 2 m plots on a Ferrosol site with digit grass used as a model plant. Manure/ sorber mixtures were applied in trenches (5 cm below surface) to these plots at increasing sorber levels at anNloading rate of 200 kg/ha. Gas produced in all experiments was plumbed into a purpose-built automated gas analysis (N2O, NH3, CH4, CO2) system. In the laboratory experiments, the sorbers showed strong capacity to decreaseNH3 emissions (up to 80% decrease). Ammonia emissions were close to the detection limit in all treatments in the glasshouse and field trial. In all experiments, considerable N2O decreases (>40%) were achieved by the sorbers. As an example, mean N2O emission decreases from the field trial phase of the project are shown in Fig. 1a. The decrease inGHGemissions brought about by the clays did not negatively impact agronomic performance. Both vermiculite and bentonite resulted in a significant increase in dry matter yields in the field trial (Fig. 1b). Continuing work will optimise the sorber technology for improved environmental and agronomic performance across a range of soils (Vertosol, Dermosol in addition to Ferrosol and Sodosols) and environmental parameters (moisture, temperature, porosity, pH).

Determination of Carbonate Rock Chemistry Using Laboratory-Based Hyperspectral Imagery

The development of advanced laboratory-based imaging hyperspectral sensors, such as SisuCHEMA, has created an opportunity to extract compositional information of mineral mixtures from spectral images. Determining proportions of minerals on rock surfaces based on spectral signature is a challenging approach due to naturally-occurring minerals that exist in the form of intimate mixtures, and grain size variations. This study demonstrates the application of SisuCHEMA hyperspectral data to determine mineral components in hand specimens of carbonate rocks. Here, we applied wavelength position, spectral angle mapper (SAM) and linear spectral unmixing (LSU) approaches to estimate the chemical composition and the relative abundance of carbonate minerals on the rock surfaces. The accuracy of these classification methods and correlation between mineral chemistry and mineral spectral characteristics in determining mineral constituents of rocks are also analyzed. Results showed that chemical composition (Ca-Mg ratio) of carbonate minerals at a pixel (e.g., sub-grain) level can be extracted from the image pixel spectra using these spectral analysis methods. The results also indicated that the spatial distribution and the proportions of calcite-dolomite mixtures on the rock surfaces vary between the spectral methods. For the image shortwave infrared (SWIR) spectra, the wavelength position approach was found to be sensitive to all compositional variations of carbonate mineral mixtures when compared to the SAM and LSU approaches. The correlation between geochemical elements and spectroscopic parameters also revealed the presence of these carbonate mixtures with various chemical compositions in the rock samples. This study concludes that the wavelength position approach is a stable and reproducible technique for estimating carbonate mineral chemistry on the rock surfaces using laboratory-based hyperspectral data.

CONVERSION OF THE LOW QUALITY INDONESIAN NATURALLY-OCCURRING MINERALS INTO SELECTIVE TYPE OF ZEOLITES BY SEED-ASSISTED SYNTHESIS METHOD

An X-ray diffraction (XRD) revealed that Indonesian naturally-occurring mineral from Nanggung, Bogor shows to be a low quality product as it does not seem to contain any zeolite materials. As located in the volcanic area, Indonesia essentially has abundant source of natural zeolites and the country has put much efforts on these treasured materials for export commodity. In order to bring the local natural mineral into high value and to discover whether the mineral has at least zeolitic fragments, we have implemented seed-assisted synthesis to see the possibility of growing zeolite and turn this mineral into high quality. In principle, once the mineral has zeolitic fragment or nuclei, recrystallization of the mineral may occur. By utilizing this mineral as seed in aluminosilicate mother solution, selective mordenite-type (MOR) zeolite can be obtained after hydrothermal treatment. Characterization by XRD showed that this MOR zeolite has high crystallinity and scanning electron microscopy (SEM) depicted the crystal morphology. The natural mineral is conclusively essential for the formation of MOR zeolite by seeding the aluminosilicate mother solution. In the absence of aluminosilicate mother solution, natural mineral can be recrystallized into selective analcime-type (ANA) zeolite. MOR zeolite is known to be useful for several applications such as catalysis whereas ANA zeolite has been considered to be less potential due to relatively small microporosity.

Stabilization of Cr(VI) from fine ferrochrome dust using exfoliated vermiculite

This study proved that vermiculite, a natural occurring mineral, can effectively remove and stabilize Cr(VI) from fine ferrochrome dust leachate. Batch adsorption studies were carried out to determine the effect of pH, contact time and adsorbent dose on the removal of Cr(VI). The process was found to be highly pH dependent. The optimum conditions for the Cr(VI) removal are at a pH of 1.5, contact time of 2h and adsorbent dose of 10gL−1. The stability of the Cr(VI)-loaded vermiculite remained unchanged after 12 months, when the vermiculite was evaluated with the ASTM and TCLP Cr(VI) leach methods. However, Cr(VI) desorption did take place when the Acid Rain Test was used. The adsorption kinetic data fits the pseudo-second order model, while the equilibrium data of Cr(VI) adsorption onto vermiculite are best described by the Langmuir isotherm. The presence of hydrobiotite and biotite in the industrial vermiculite slightly decreased the degree of adsorption of Cr(VI).

Review on shilajit used in traditional Indian medicine

Shilajit is a multi-component natural occurring mineral substance used in Ayurveda and Siddha systems of medicine which originated in India. Its source can be traced to the mountainous regions, where the hilly tribes first identified its beneficial use. Shilajit is aptly referred to as 'rasayana'/'rasayanam' in Ayurveda and Siddha literature which means rejuvenator because it prevents ailment and enhances the quality of life. An attempt has been put forth to review shilajit pertaining to its origin, synonyms, varieties, physical properties, chemical constituents, therapeutic properties and important biological properties to affirm its rasayana property. All relevant information on shilajit was collected from classical texts including pharmacopoeias, formularies, etc. Moreover, select doctoral thesis from Banaras Hindu University, Varanasi and Gujarat Ayurved University, Jamnagar were also scanned. Published papers on shilajit were collected from important databases for biomedical sciences. Amongst, the various biological properties of shilajit, antioxidant activity and immuno-modulatory activity were focused as it is closely related to its rasayana potential. This review finds that shilajit is used in twenty Sastric formulations and twenty-four proprietary drugs for extraneous indications. Even-though, there is a long history of use of shilajit in traditional Indian materia medica, shilajit unfortunately lacks scientific evaluation and systematic documentation. In vivo antioxidant activity of shilajit has been studied at an irrelevant dose and without using a positive control. The immuno-modulatory activity does not stand the test of critical assessment and currently may be considered as unproven. Based on the earlier studies, the bioactivity of shilajit lacks substantial evidence. Nevertheless, further studies are imperative to overcome the lacuna in establishing the antioxidant property of shilajit and more specific assays are needed to vouch shilajit as an immuno-modulator which may be of use to establish its rasayana potential.