Buerger (Zeits. Krist., 1957, vol. 109, p. 42) describes an algorithm for deriving data for the reduced unit cell from those obtained for an arbitrary crystal setting. It is shown that indices can be added to the algorithm so that one also derives the transformation matrix for the change of setting. Conversely, a known transformation matrix forms a set of instructions for using the algorithm to transform unit cell data, whether X-ray or morphological, from the initial to the final setting, One can thus use the algorithm to calculate the lengths of any unit cell vectors and the angles between them, and, using reciprocal cell data, to obtain any interfacial angles. Worked examples of these applications show that the proposed calculation method is shorter and simpler than those at present accepted.

The water vapour released upon heating the specimen is driven through a water absorber. The intensity of the exothermic reaction produced by absorption of the water is recorded against the temperature of the specimen. A series of curves obtained with various clay minerals are presented to illustrate the method. The significance of results in the identification of the clay minerals and the determination of their structure is considered.

The mass suseeptibility of 23 analysed or partially analysed garnets has been measured by means of a calibrated Franz Isodynamic magnetic separator. Straight lines are fitted to the adjusted data for mass susceptibility and molecular composition. The mass susceptibilities of the theoretical end-members in electromagnetic units × 106 are estimated as: almandine, 68±2 e.m.u.; spessartine, 81±3 e.m.u.; and andradite, 49±3 e.m.u. Grossular and pyrope are assumed to have susceptibilities of nil.

A new occurrence of holmquistite is described. The mineral is found in amphibolite at the contact of a lithium pegmatite. Chemical analyses and optical data of the holmquistite and an associated hornblende are given.

Psilomelane has been shown to be orthorhombic with a 8·254, b 13·40, c 2·864 Å. by the application of Lipson's method. The indexing of powder photographs of psilomelane , where R″ includes the bivalent metals Mn, Ba, Ca, Mg, Co) indicates the space-group P21212 (D22) with one molecule per unit cell. Indexing of powder photographs of psilomelane is not satisfactory with Vaux's axes. Fermor's ‘psilomelane’ is cryptomelane, which is tetragonal with a 9·822, c 2·858 Å. Cryptomelane (KR8O16, where R stands for Mn in different valency states, partly replaced by other cations) is body-centred tetragonal with one molecule per unit cell. Fermor's stalactitic ‘psilomelane’ has an inner dull core of cryptomelane and an outer fine-grained crust of pyrolusite in each needle-shaped body.

The observed order of importance of the forms of baryte, anglesite, and celestine is first determined by a modification of the methods used by Donnay and Harker. Their hypothesis is applied to determine the space-groups of these minerals by morphological means, and a comparison is made of the observed and theoretical orders of importance of forms in these minerals. It is concluded that agreement is poor between the observed and predicted frequencies of forms in the baryte group. The rank distribution of some of the more important forms is presented graphically.

Secondary minerals described from Tertiary amygdaloidal basalts in the Hunter Springs area, Barrington, New South Wales, are regarded as having been deposited from cold solutions some considerable time after consolidation of the basalts. The constituents in the solutions were evidently derived from the basalts by the action of circulating meteoric waters rather than by deuteric activity.

An examination of available chemical analyses shows that the anthophyllite and cummingtonite series of amphibole minerals are not isodimorphous. Whilst the anthophyllites are truly lime-free amphiboles, small amounts of calcium are essential to stabilize the monoclinic lattice of cummingtonites, which should be regarded as lime-poor amphiboles, analogous to the lime-poor pyroxenes. The existence of synthetic clino-anthophyllites is considered.

Sepiolite found as a minor constituent of dolomitie marble bordering tremolite rock from the southern contact zone of the Quérigut granite is briefly described and optical data are presented. A possible paragenesis, following on break-down of the tremolite under the action of carbon dioxide, is suggested.

A number of secondary minerals have grown in recent years in a part of the Billingham anhydrite mine, by evaporation of water from the Upper Magnesian Limestone, and include some unusual species, the most interesting of which is thought to be ilsemannite.

A new occurrence of helvine, the rare manganese end-member of the helvine group, is described. The mineral is found in a granite pegmatite associated with microcline-perthite, petalite, spodumene, muscovite, and spessartine. A chemical analysis of the mineral is given.