The history of the chemical analysis of minerals is shortly reviewed. Following rapid developments between 1770 and 1810, few important changes took place for close on 130 years; new procedures led to simpler and more convenient separations but not, on the whole, to greater accuracy. The older analyses are, in general, neither worse nor better than modern ones, and analyses can only be assessed on internal evidence, if available, or on the reputation of the analyst.

The development of microchemical and colorimetric techniques in the last 40 years has resulted in a great reduction in the amount of material required for a mineral analysis; 5 to 20 mg is usually sufficient, and in favourable cases a complete analysis may be possible on less than I mg. Some modern instrumental methods are considered, and it is concluded that they cannot wholly replace the classical wet-chemical methods in their modern developments.

W. F. Hillebrand (1894) deplored the tendency of some petrologists to demand large numbers of very incomplete rock analyses, and his remarks are considered apposite today.

A metallic mass brought to the Western Australian Museum from the Wongan Hills district N.W. of Perth has been identified as an iron meteorite of unique type. It has graphite inclusions about I mm across distributed throughout the metal giving a ‘raisin bread’ appearance. Its nickel content (6·65 %) is comparable with that of coarse octahedrites but the kamacite grain structure is anomalous. Its gallium, germanium, and nickel contents place it close to, but outside, Wasson's chemical group IIb. Taenite is absent and troilite is rare. Neumann bands in the kamacite are distorted and the kamacite has flowed around large schreibersite inclusions. The latter have an exceptionally low nickel content (7·0 %) and probably formed at an unusually high temperature. The kamacite contains more phosphorus than normal iron meteorites, and small schreibersite grains in the kamacite are relatively nickel-poor (22 %). The unusual structure of this iron is thought to be due to one or more of the factors high carbon, high phosphorus, and relatively rapid cooling.

Three-dimensional counter-diffractometer data and a full-matrix least-squares method have been used to refine the crystal structure of a ferrotschermakite in the space group C2/m. The chemical composition of the amphibole is with cell parameters a 9·8179(7), b 18·1060(14), c 5·3314(5) Å, and β 105·00(I). Cation site-occupancies were initially assigned by ionic-radius criteria and refined with the constraint that the sum total of the site-occupancies be equal to the chemical analysis.

The A-site shows positional and substitutional disorder and can be better represented by two sites, one on the mirror plane and the other on the 2-fold axis.

Unit weights were used throughout the refinement and the final R-factor for 1207 observed nonequivalent reflections was 4·5 %.

Hematophanite, ideally Pb4Fe3O8Cl, is tetragonal, space group P4mm, with a = 3·92 and c = 15·31 Å. The crystal structure, which has been refined to an R-factor of 9·1 %, may be described as an interlayering of perovskite-like units with a cesium chloride or, alternatively, a nadoritelike unit. The nadorite-like part consists of a double layer of PbO4Cl4 distorted square antiprisms. Iron atoms are in 6-fold (tetragonal bipyramidal) and 5-fold (square pyramidal) coordination.

A new example of the Nevada twin from the Mont-Dore (Massif Central, France) is described. A structural interpretation of the twin is given assuming a (01) composition plane parallel with the chains of the feldspar structure.

Occurrence and major- and minor-element compositions of chlorites from plutonic rocks of the central Sierra Nevada batholith have been studied in detail.

Chlorite has formed largely as an alteration product of biotite, presumably late in the magmatie history of the granitic rocks as a result of subsolidus reaction. Major-element composition of chlorite is strongly influenced by composition of coexisting biotite. Minor-element differences between the two minerals can, for the most part, be attributed to structural differences. The minor-element data, particularly for Cu, indicate that the process of chloritization is not a likely mechanism for release of ore metals from primary minerals.

Heyite occurs in silicified limestone with other oxidation-zone minerals derived from galena, chalcopyrite, and pyrite. The occurrence is near Ely, Nevada. Most common are pyromorphite, cerussite, and chrysocolla. Heyite occurs on and replaces corroded tungstenian wulfenite. Crystals are small (up to 0·4 mm), simple in habit, and monoclinic. Only {001}, {100}, {110}, and {01} have been observed. Twinning on {110} is relatively common. The colour is yellow-orange with a yellow streak, H = 4. Electron probe analyses (average of three) gave PbO 75·4 %, ZnO 0·81 %, FeO 8·41 %, V2O5 12·65 %. This leads to Pb5(Fe,Zn)2(VO4)2O4, with Z = 1.

The space group is P21/m. Cell constants, refined from powder data, are a 8·910 Å, b 6·017, c 7·734 (all ±0·004 Å); β III° 53′±4′. The strongest powder lines (Cr-Kα) are: 3·248, 11, (100); 2·970, 30, 21 (69); 2·767, 211 (61); 4·873,110, (46); 3·674, 111, (35); 2·306 (33); 3·010, 020, (29); 3·412, 20, 11, (25); 8·281, 100, (25); and 2·113 (20). Gcalc 6·284, Gmeas 6·3±0·2 Optically biaxial with 2Vγ 82°calc, 89°meas; αD 2·185, βD 2·219, γD 2·266; all values ±0·01 and determined in S-Se melts. Dispersion is weak with π > ν. The orientation is β = b, α: [001] 36° (in obtuse β). Nonpleochroic.

Three small specimens were found, and represent a total of less than 100 mg of the mineral. One has been deposited with the British Museum (Natural History). The name is for Dr. Max Hey, eminent British chemist and mineralogist.

The cell is strikingly similar to that of brackebuschite but electron probe examination of a newly analysed (by atomic absorption) specimen of the latter from the type locality in Argentina shows a marked chemical difference. Heyite strongly resembles descloizite in appearance.

Heyite (see preceding paper) is so strikingly similar to brackebuschite that a close comparison of the two species seemed advisable. Topotype brackebuschite (B.M. 55819) was used for this purpose.

Brackebuschite is a vanadate of lead, manganese, and iron, heyite a vanadate of lead and iron. Both species are monoclinic with diffraction symmetry P21 or P21/m. The X-ray cells are remarkably close: a = 8·810, 8·910; b = 6·155, 6·017; c = 7·651, 7·734; β = 111° 30′, 111° 53′ (brackebuschite first). As might be expected, powder patterns are strikingly close as well.

Other than the similarities noted above, the minerals differ so fundamentally that they cannot be the same—they are valid and distinct species. Optic orientations show α: [001] 20° (in acute β) for brackebuschite, 36° (in obtuse β) for heyite. Indices are (brackebuschite first): α 2·28, 2·185; β 2·38, 2·219; γ 2·49, 2·266 for the sodium D line.

Chemical differences are irreconcilable and reaffirm brackebuschite as Pb2(Mn,Fe,Zn)(VO4)2.H2O while heyite is Pb5Fe2(VO4)2O4.

The chemical analyses, structural formulae, and optical data of seven orthopyroxenes and six clinopyroxenes, all from the charnockite series of Amaravathi, are presented. The orthopyroxenes are in the hypersthene-ferrohypersthene range while the clinopyroxenes are in the sahlite range. The aluminous nature of the pyroxene is believed to be the result of high pressure. The clinopyroxenes have the granulite trend on the Wo-En-Fs plot. The tie-line projections and the KD values for the pyroxene pairs indicate conditions of chemical equilibrium around 670 °C for the charnockite series of Amaravathi.

Silicate minerals show several correlations between structure type and elastic constants. Stiffness coefficients are generally larger in the direction of Si-O bonding. A simple mechanical analogy in which atomic bonds are simulated by springs connected in series and parallel is used to estimate the size and anisotropy of the elastic moduli and their pressure derivatives.

Garnet porphyroblasts, containing elongate ilmenite inclusions arranged in an essentially spherical pattern, are described. The garnets are post-tectonic, and the inclusion pattern is the result of deformation and simultaneous replacement of the matrix by the growing porphyroblast.

Infrared absorption spectra of the precipitated solids separated from aluminium-hydroxide solutions below the pH of minimum solubility of Al(OH)3 demonstrate the slow ageing of polymeric Al complexes to gibbsite. On comparison with the spectra of natural gibbsites, shifts in absorption frequency during crystal growth are interpreted in terms of changes in hydrogen bonding as a consequence of deprotonation and stacking of aluminium hydroxide layers to form gibbsite. In alkaline solutions the bayerite polymorph precipitates and IR frequencies are compatible with protonation as aluminate ions associate with the bayerite crystal having a lower crystal energy than its low pH polymorph. The infrared spectrum of nordstrandite, which is probably the stable polymorph in alkaline solution, shows evidence of strongly polarized hydroxyl ions similar to gibbsite.

Eight new and fourteen published analyses of astrophyllites are used to examine chemical variation within the group. Al, Ca, Cs, F, Mg, Mn, Nb, Rb, Sn, Zn, and Zr may all substitute in moderate to large amounts in the unit cell, whose basic formula is (K,Na)3Fe7Ti2Si8(O,OH)31; the natural Mn- and Nb- analogues of astrophyllite have been recorded. Ba, Cl, Cu, Li, P, Pb, Sr, and Ta are present, but in smaller amounts. The majority of specimens show appreciable cation deficiencies, up to 5 % of sites remaining vacant. Astrophyllites from undersaturated igneous rocks are characterized by higher Al, Ca, Mg, Mn, (OH+F), (K+Na) and Zr, and lower Li, Pb, and Zn contents than those from oversaturated igneous rocks. A ‘high-alkali’ type of astrophyllite is distinguished. A new occurrence of nigerite is noted.