Spurrite-bearing contact-metasomatic mineral assemblages occur with a few of the many rhyolite stocks intrusive into Georgetown (Cretaceous) limestone in the Encantada district of northern Coahuila, Mexico. The contact-metasomatic suites are found associated only with rhyolites that solidified within the thick Georgetown limestone. Rhyolites that penetrated through the limestone have sharp contacts commonly marked by perlitic contact breccias. The structural form of all the rhyolites indicates intrusion under high pressure.

Three distinct contact-mineral suites have been recognized: Foliated garnetwollastonite rocks occur adjacent to the rhyolite, whereas spurrite is only found further from the intrusive. The inner side of the spurrite-bearing zone is characterized by foliated spurrite-garnet-periclase rocks, whereas the outer side of the spurrite zone consists of a massive, coarse-grained, spurrite-rankinite-periclase rock, which has a sharp contact with the outermost foliated marble zone. At one location, massive spurrite occupies ‘dikes’ radial to the intrusive, which are post-dated by wollastonite-bearing gehlenite-diopside rocks.

It is concluded that the stages of rhyolite emplacement include: First, preliminary high-pressure structural site preparation accompanied by intrusion of rhyolite and metasomatic introduction of Si and Al into preheated cap rock. Then crystallization of the metasomatic zone, under conditions of upward pressure exerted by the rhyolite, to give the features of the spurrite zone; followed by conversion of the inner side of the spurrite zone to a wollastonite-bearing assemblage.

The composition of carphosiderite has been given as

H2O.Fe3(SO4)2(OH)5H2O

and like the jarosites is characterized by a ferric iron to sulphate ratio of 3:2. It is significant not only that this formula was worked out on artificial material but also that none of the analyses so far made supports it. The present investigation shows that there is little or no evidence for the existence of a mineral with the above composition and that carphosiderites are in reality either jarosite or natrojarosite. It has long been thought that certain other minerals, namely borgströmite, utahite, cyprusite, pastréite, raimondite, apatelite, and planoferrite, were similar to, if not identical with, carphosiderite and six of these are listed with carphosiderite in Dana, Syst. Min., 7th edn. These minerals with the exception of planoferrite and the possible exception of apatelite are also jarosite or natrojarosite.

In the course of a petrological examination of some hundreds of specimens from the Tertiary coastal dike swarm of east Greenland, collected at various times by L. R. Wager and W. A. Deer, it was decided to investigate the nature of the residual glassy mesostasis of one of the olivine-tholeiites, in the hope that it might shed some light on the trend of differentiation of the magma responsible for the bulk of the rocks in the swarm. An account of the petrology of the swarm as a whole will be published in due course, but it was thought that a note on the chemical and physical properties of this glassy residuum might be worthy of independent publication, particularly as it provides an interesting comparison with the results of work carried out by Walker (1930, 1935) on the residual glass from one of the Upper Carboniferous tholeiites from central Scotland. The general features of the east Greenland coastal dike swarm have already been described by Wager and Deer (1938) and Wager (1947).

The new mineral, gysinite-(La), with the ideal formula PbLa(CO3)2(OH)⋅H2O, has been discovered in lujavrite from the Saima alkaline complex, Liaoning Province, China. It commonly occurs as subhedral to anhedral, granular and platy crystals of 5 to 50 μm in size, in interstices or enclosed in microcline, aegirine and nepheline. Associated minerals include nepheline, aegirine, microcline, natrolite, eudialyte, lamprophyllite, bastnäsite-(Ce), parasite-(Ce), ancylite-(La), ancylite-(Ce), bobtraillite, britholite-(Ce), thorite, calcite and galena. The crystallisation of gysinite-(La) may be related to the post-magmatic carbonation event. Gysinite-(La) crystals are generally transparent, colourless, or pale yellow, with a vitreous lustre and white streak. It is brittle with an uneven fracture, and the estimated Mohs hardness is 3½ to 4. The calculated density is 5.007 g/cm3. Optically, gysinite-(La) is biaxial (–), α= 1.832(2), β= 1.849(4), γ = 1.862(5) in white light and 2Vmeas = 81.6°. The empirical formula of gysinite-(La) is (La0.93Pb0.61Nd0.23Pr0.14Sr0.04Gd0.02Sm0.01Eu0.01Ca0.01)Σ2(CO3)2(OH)1.34⋅0.66H2O, which is calculated on the basis of general formula (REExM2+2–x)(CO3)2(OH)x⋅(2–x)H2O. The strongest eight lines of its powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 5.596 (21) (011), 4.349 (100) (110), 3.732 (68) (111), 2.984 (61) (121), 2.667 (21) (031), 2.363 (48) (131), 2.090 (29) (221) and 2.028 (21) (212). Gysinite-(La) is orthorhombic, in the space group Pmcn, and unit-cell parameters refined from single-crystal X-ray diffraction data are: a = 5.0655(2) Å, b = 8.5990(3) Å, c = 7.3901(4) Å, V = 321.90(2) Å3 and Z = 2. It is a new member of the ancylite group and isostructural with gysinite-(Nd), but with La and Pb dominant in the metal cation sites in the structure.

Cadmium sulfide mineralization occurs in grey-black shales of the late Mesoproterozoic Stoer Group, Torridonian Supergroup, northwest Scotland. Cadmium is strongly redox-controlled, and normally concentrated in anoxic marine sediments or epigenetic mineralization involving organic matter. However the Stoer Group was deposited in a terrestrial environment, including lacustrine deposits of shale. At the limited levels of atmospheric oxygenation in the Mesoproterozoic (∼10% of present), the near-surface environment could have fluctuated between oxic and anoxic, allowing fractionation of Cd from Zn, and the formation of Cd sulfide rather than Cd-bearing sphalerite. This occurrence emphasizes the importance of the Stoer Group as a record of the Mesoproterozoic terrestrial environment.

The mineral howieite has a stability range that extends down to pressures at, or even below, those normally considered to represent blueschist facies metamorphism. Its structure, lying somewhere between a chain and a sheet silicate, can accommodate almost complete iron for manganese substitution as well as the more extraordinary ferrous iron for ferric iron substitution, that is tolerated by changes in the hydroxyl and water content of the unit cell. The ideal formula is NaM12 Si12(O,OH)44, where M is principally manganese and iron but may include limited amounts of aluminium and magnesium. Four new localities for howieite have been discovered by the author and the howieites from the eight localities that have been analysed here help complete the compositional spectrum. The most curious crystallographic feature of howieite is that although the structure seems capable of considerable chemical variation, it is only those howieites of approximate NaMn3Fe8(AlMg)1Si12(O,OH)44 composition that are well crystallized, often growing to over 10 mm in length.

A spherulitic mineral occurring as veins and nodules in celestine-bearing secondary limestones in the Lower Purbeck Beds at Durlston Head, Swanage, Dorset, is identified as calciostrontianite, a mineralnot previously recorded from Britain. Textural relationships indicate that it was formed from the alteration of celestine and was in part converted back into celestine. The calciostrontianite originated as an epigenetic mineral during the tectonic movement that gave rise to the Broken Beds.

The mineral now briefly described occurs as a rare constituent of the zone of hybrid rocks formed by assimilation of limestone by the dolerite intrusion at Scawt Hill, Co. Antrim. It is found particularly in intimate association with the melilite-bearing types of this hybrid zone and is a constituent of some of the late-formed vesicles in these rocks. The minerals associated with it in the vesicles are chiefly calcite, thomsonite, and another zeolitic mineral as yet undetermined. These vesicles are most frequently enclosed by a ground rich in melilite, or they may occur within large crystals of melilite. In some cases the mineral forms minute venules cutting through the melilite, suggesting that it is derived in part by attack of residual solutions upon the melilite itself. All the evidence clearly indicates that the mineral is among the latest products of consolidation of the hybrid zone.

The provenance of raw materials and finished objects is one of the most intriguing problems in archaeology. It is significant for the discussion of inter-regional cultural communication. Many of the methods used to determine provenance employed by archaeologists are shared with geologists or geochemists, among which the use of lead isotopes is probably one of the best-known. However, geologists and archaeologists do not always ask the same questions. Because of many and various human choices, it is not always possible to apply geological methods directly to archaeological objects. Specifically, the potential existence of mixing and recycling of metals challenges all the provenance studies of metal objects. In this paper, using Bronze Age China as an example, we suggest that by using geochemical techniques such as lead isotopic analysis and trace-element analysis of bronzes, but by asking slightly different questions, one can throw new light on the way in which important resources were managed by consumers of different social status within early dynastic China.

The occurrence of acmitic pyroxenes in the post-Cambrian intrusions of the north-west of Scotland was first noted by Teall (Home and Teall, 1892) who recorded aegirine in two dikes discovered by Gunn in the Coigach district of Ross-shire, and aegirine-augite in the borolanite of the Cnoc-na-Srbine mass. Since then, acmitic pyroxenes have been recorded by Teall (1900) from the Assynt felsites, Shand (1910) from dikes of the border zone of Cnoc-na-Srbine, and Phemister (1926) from the dikes and plutonic rocks of the Loch Ailsh laccolite.

Having undertaken a comprehensive examination, in the field and in the laboratory, of the post-Cambrian sills and dikes of the Assynt district, the writer determined some of the optical constants of the acmitic pyroxenes of these intrusions. Arising from this work the considerable data now available on the acmitic pyroxenes has been reviewed. A chemical analysis has also been carried out, and it is hoped that the information assembled and re-interpreted here may be of some general interest.

The margarosanite group (now officially confirmed by IMA-CNMNC) consists of triclinic Ca-(Ba, Pb) cyclosilicates with three-membered [Si3O9]6– rings (3R), with the general formula AB2Si3O9, where A = Pb, Ba and Ca and B = Ca. A closest-packed arrangement of O atoms parallel to (101) hosts Si and B cations in interstitial sites in alternating layers. The 3R layer has three independent Si sites in each ring. Divalent cations occupy three independent sites: Ca in B occupies two nonequivalent sites, Ca1 (8-fold coordinated), and Ca2 (6-fold coordinated). A (=Ca3) is occupied by Pb2+ (or Ba2+) in 6+4 coordination, or 6+1 when occupied by Ca; this third site occurs within the 3R-layer in a peripheral position. Three minerals belong to this group: margarosanite (ideally PbCa2Si3O9), walstromite (BaCa2Si3O9) and breyite (CaCa2Si3O9). So far, no solid solutions involving the Ca1 and Ca2 sites have been described. Therefore, root names depend on the composition of the Ca3 site only. Isomorphic replacement at the Ca3 sites has been noted. We here report data on a skarn sample from the Jakobsberg Mn–Fe oxide deposit, in Värmland, Sweden, representing intermediate compositions on the walstromite–margarosanite binary, in the range ca. 50–70% mol.% BaCa2Si3O9. The Pb-rich walstromite is associated closely with celsian, phlogopite, andradite, vesuvianite, diopside and nasonite. A crystal-structure refinement (R1 = 4.8%) confirmed the structure type, and showed that the Ca3 (Ba, Pb) site is split into two positions separated by 0.39 Å, with the Ba atoms found slightly more peripheral to the 3R-layers.

The new mineral fluorapophyllite-(NH4), ideally NH4Ca4(Si8O20)F⋅8H2O, was found at the Vechec andesite quarry located near Vechec village, Vranov nad Topľou Co., Prešov Region, Slovak Republic. It occurs in cavities of quartz–illite–saponite–tobelite xenolith embedded in pyroxene andesite. Fluorapophyllite-(NH4) is associated with calcite, tridymite, pyrite, chabazite-Ca and heulandite-Ca. It forms clusters, aggregates or crystalline crusts consisting of individual, well-developed crystals up to 4 mm in size, exhibiting the forms {110}, {101} and {001}. The mineral is colourless to light pink and translucent with white streak and vitreous to pearly lustre; it is non-fluorescent under ultraviolet radiation. The Mohs hardness is ~4½ to 5, tenacity is brittle, fracture is irregular, and there is perfect cleavage on {001}. The calculated density is 2.325 g cm–3. Fluorapophyllite-(NH4) is optically uniaxial (+) with ω = 1.5414(5) and ɛ = 1.5393(8) (λ = 589 nm). It is non-pleochroic. The empirical formula (based on 29 O + F apfu) is [(NH4)0.55K0.32Na0.07Ca0.06]Σ1.00(Ca4.01Mg0.02)Σ4.03Si7.97O20[F0.84(OH)0.16]Σ1.00⋅8H2O. Fluorapophyllite-(NH4) is tetragonal, space group P4/mnc, a = 8.99336(9) Å, c = 15.7910(3) Å, V = 1277.18(3) Å3 and Z = 2. The seven strongest X-ray powder diffraction lines are [dobs in Å,(I,%)(hkl)]: 7.897(32)(002), 7.812(13)(101), 4.547(14)(103), 3.946(100)(004), 2.985(39)(105), 2.4841(11)(215) and 1.5788(12)(00.10). The crystal structure of fluorapophyllite-(NH4), refined to R1 = 0.0299 for 743 unique (I > 3σI) observed reflections, confirmed that the atomic arrangement is very similar to that of the other members of the apophyllite group. The new mineral is named according to the current nomenclature scheme for apophyllite-group minerals and is an NH4 dominant analogue of fluorapophyllite-(K), fluorapophyllite-(Na) and fluorapophyllite-(Cs).

An apparatus is described for the measurement of the rates of fast precipitation reactions. It consists of a T-tube, where reactants are added to the arms of the T, mixed rapidly at the junction, and the rates of disappearance of reactants or appearance of products are measured along the stem of the T. The geometry of the system results in a steady state being established in the apparatus, enabling detailed analysis of reaction progress. The apparatus has been used to investigate the kinetics and mechanism of iron sulphide precipitation reactions. It has enabled measurements to be made with relatively high precision and good accuracy of the first 130 ms of reaction time.

Two new members of the atacamite family were discovered recently in the Sadamisaki Peninsula, Ehime Prefecture, Japan. Iyoite, MnCuCl(OH)3, is an Mn-Cu ordered analogue of botallackite, while misakiite, Cu3Mn(OH)6Cl2, is an Mn-rich analogueof kapellasite. Both minerals occur in manganese ore crevices in close association with one another. Iyoite forms radial and dendritic aggregates consisting of pale green, bladed crystals. Misakiite commonly exists in emerald green, tabular, hexagonal crystals. The densities of iyoite andmisakiite were calculated to be 3.22 and 3.42 g cm–3 based on their empirical formulae and powder X-ray diffraction data. Under the same axial setting of botallackite, iyoite is monoclinic, space group P21/m, a = 5.717(2), b = 6.586(2), c= 5.623(3) Å, β = 88.45(3)° and V = 211.63(15) Å3. Misakiite is trigonal, space group P3m1, with a = 6.4156(4), c = 5.7026(5) Å and V = 203.27(3) Å3. The structures of both mineralsare classified as layer type and the two are closely related. These new minerals were formed by the reaction between seawater and naturally-occurring manganese ores including native copper. These minerals are challenging to produce synthetically. Misakiite was synthesized successfully usinga hydrothermal method, while iyoite could not be made.

Two crystals of the uranyl carbonate mineral grimselite, ideally K3Na[(UO2)(CO3)3](H2O), from Jáchymov in the Czech Republic were studied by single-crystal X-ray diffraction and electron-probe microanalysis. One crystal has considerably more Na than the ideal chemical composition due to substitution of Na into KO8 polyhedra; the composition of the other crystal is nearer to ideal, and similar to synthetic grimselite. The presence of Na atoms in KO8 polyhedra, which are located in channels in the crystal structure, reduces their volume, and as a result the unit-cell volume also decreases. Structure refinement shows that the formula for the sample with the anomalously high Na content is (K2.43Na0.57)Σ3.00Na[(UO2)(CO3)3](H2O). The unit-cell parameters, refined in space group P2c, are a = 9.2507(1), c = 8.1788(1) Å, V = 606.14(3) Å3 and Z = 2. The crystal structure was refined to R1 = 0.0082 and wR1 = 0.0185 with a GOF = 1.33, based on 626 observed diffraction peaks [Iobs>3σ(I)].