Xocomecatlite and tlalocite were found at the Bambollita mine near Moctezuma, Sonora. Xocomecatlite is probably orthorhombic, and an indexed cell based on the powder data gave a 12.140 A, b 14.318, c 11.662. Based on this cell, the empirical contents are Cu36.6 Zn1.7 (TeO4)12.5 (OH)51.6 or Cu3TeO4(OH)4. Tellurate was found both microchemically and by spectrophotometry. Colour rich green (R.H.S. 132A) with pale streak, H = 4. Optically negative with α = 1.775, β = 1.900, γ = 1.920. G = 4.65.

Tlalocite is optically orthorhombic but the cell could not be indexed; only powder data are presented. Chemical analysis showed both tellurite and tellurate and led to the formula

Colour pale blue (R.H.S. 121A) with a whitish streak; H = 1, gummy and sectile. G = 4.55.

Plotting stability fields for various Te species at 25°C in terms of Eh and pH showed that TeO42−.aq can exist in nature over a wide pH range, but only under extreme conditions of oxidation.

Creaseyite was first noted in specimens from Tiger, Arizona, and was then found at Wickenburg, Arizona, and Caborca, Sonora, prior to description. It is an oxide zone mineral occurring with wulfenite, willemite, mimetite, chrysocolla, wickenburgite, and ajoite. The composition is [Cu2Pb2(Fe,Al)2Si5O17-6HaO]. Colour Agathia green (R.H.S. 142B) with pale streak, H = 2½, Dmeas = 4.1, calc. 4.01. Crystals are orthorhombic with a 12.483, b 21.395, c 7.283. Z = 4.2Vγ 69° meas; α 1.737, β 1.747, γ 1.768.

An electron-probe microanalysis of tetrahedrite occurring together with the latest-deposited pyrite-cinnabar association in the Chiprovtsi lead-silver deposit yielded more than 16 wt. % Ag and more than 18 wt. % Hg. X-ray powder examination established an extremely large unit-cell edge, a 10.64±0.01 Å. Vickers microhardness 223 to 237 kg/mm2. The chemical formula derived on the basis of the analyses made is quite near to Cu6+(Cu+, Ag+)4(Hg,Zn)2(Sb,As)4S13. There is not any antiparallelism between Ag and Hg in tetrahedrite. The name proposed for all stages of simultaneous isomorphic replacement along the Cu+-Ag+ and Cu2+-Hg2+(Zn2+,Fe2+) directions is argentian mercurian tetrahedrite. The upper limits of the Ag and Hg content are expected to be Cu6Ag4Hg2(Sb,As)4S13. It is the six copper atoms (Cu4+;Cu22+), sited in the Laves’ polyhedra, that are replaced by Ag+ and Hg2+ respectively.

Lepidomelane, an iron-rich biotite, was heated in air or in vacuum, or by electron bombardment, and the processes of dehydration and transformation were studied by means of X-ray diffractometry, optical microscopy, and electron microscopy. By heat treatment, vacancies are at first formed by the evaporation of water molecules and alkali ions, and they move and condense to form holes, which act as preferential nucleation sites for new phases. Other preferential sites are edges of exposed silicate sheets along microcracks, and these are decorated by a newly formed maghemite- like mineral whose a is 10.20 Å (on a hexagonal cell), so that the sites can be clearly seen even under the reflection microscope. By heating at higher temperatures or prolonged heating, various phases, olivine, hematite, magnetite, and leucite are formed, depending upon the conditions of dehydration.

Native nickel of composition Ni 96.3 %, Fe 1.77 %, and Co 0.69 % was found as tiny flakes up to 0.75 mm across in a heavy mineral concentrate from stream sediments in the Jerry River, South Westland, New Zealand. The locality is approximately 13 km downstream from the original locality for awaruite (Ni2Fe), and it is shown that the nickel content of detrital grains increases with distance from the source of the awaruite in serpentinites of the Red Hills Range. It is proposed that the native nickel has been derived from awaruite by leaching of iron.

Phosphates introduced into the et-Tabun cave as a result of human habitation, mainly as bone material, were partly dissolved by slightly acid solutions (organic acids derived from human or other animal activity). From these solutions, dahllite precipitated when the solutions came into contact with calcite. In the more weathered parts of the section, where little or no calcite occurs, the phosphate minerals formed are montgomeryite and crandallite.

The Kangerdlugssuaq late dike swarm, which strikes at a high angle to the well-known East Greenland coastal swarm, is described and chemical analyses presented. The basic members are characterized by a high potassium content. A variety of kaersutite-bearing gabbroic inclusions in one member of this swarm is described in detail and microprobe analyses of clinopyroxenes, amphiboles, plagioclases, sheet silicates, and spinel minerals are presented. On the basis of this evidence it is deduced that these inclusions derive from a cumulate sequence formed at depths of between 5 and 10 km beneath the Lower Tertiary land surface. It is likely that fractionation of such assemblages causes a transition, at relatively low pressure, from undersaturated to oversaturated compositions, but the products appear to be quantitatively minor.

When magmatic fractionation involves the settling and removal of crystals from the body of magma, the efficiency of the fraetionation process may be defined as the degree of separation of the solid from the liquid phase. An expression is given that relates efficiency to the amount of mesostasis, or crystallized trapped liquid, in an igneous cumulate. The uranium contents of samples from a 349-m-long drill-core of part of the lower and hidden zones of the Skaergaard intrusion are used as a quantitative indicator of the amounts of mesostasis in the cumulates. There are marked changes in the amount of mesostasis over the length of the core and the average efficiency of fractionation was 85 %.

The granites of Sardinia have been analysed for copper, lead, and zinc, and each element has been found to show a regional variation. There is a close relationship between the copper and lead contents of the granites and the distribution of copper and lead mineralization in the island, but very little relation between the zinc contents of the granites and the distribution of zinc mineralization. This is attributed to a greater degree of lithophile character of zinc in the magmatic source region.

Fibrolitic sillimanite in some high-grade gneisses from Broken Hill, Australia, shows microstructural features suggestive of compatibility with the main coarser-grained assemblage, namely: framework-silicate interfaces either meet (110)-sillimanite/framework-silicate interfaces at approximately 90° or are attached to the ends of 'fibrolite' rods; framework-silicate interfaces are deflected by 'fibrolite' grains; and interfaces of inclusions of one framework silicate in another are deflected by 'fibrolite' grains, producing irregular, rather than rounded, inclusion shapes. These criteria suggest that the 'fibrolite' in some rocks is a compatible member of the main metamorphic assemblage. Its persistence as small grains may be due to a high proportion of relatively low-energy prismatic boundaries in the fibrolitic aggregates.