Kidwellite, NaFe93+(OH)10(PO4)6·5H2O, monoclinic, Z = 2, a = 20·61(7) Å, b = 5·15(1) Å, c = 13·75(6) Å, β = 112·64(15)·, space group A2/m, Am, or A2, is a new species that occurs in moderate abundance as a late-stage mineral associated with rockbridgeite, dufrenite, beraunite, and strengite in novaculite deposits. Colour lively pale chartreuse-green, to greenish-yellow, greenish-white, and bright yellow. H = 3, lustre silky, streak yellow, cleavage {100} perfect, habit acicular elongated parallel to [010], flattened on {100}, biaxial (−), α = 1·787(5), β = 1·800(5), γ = 1·805(5), 2V large, β∥b, not discernibly pleochroic.

The mineral is moderately widespread as a replacement of rockbridgeite and beraunite from the Ouachita Mountains, Arkansas; Indian Mountain, Alabama; Irish Creek, Virginia; Waldgirmes, West Germany. A related, but apparently distinct, species is also noted from the McMahon pegmatite, South Australia, and the Sapucaia pegmatite, Minas Gerais, Brazil.

This NW.-SE. dyke comprises two texturally distinct tholeiitic members. The outer (earlier) bears porphyritic plagioclases with essential olivine, plagioclase, and augite in a chloritized mesostasis; the inner carries porphyritic plagioclases in an olivine-free matrix showing ophitic and intersertal textures and disseminated varioles. The outer component had little metamorphic effect on its country-rock, but where the inner transgresses the outer to come into contact with the schistose-grits the latter are transformed to buchite. The outer component, after initial chilling, crystallized as a virtually closed system; the inner, on the contrary, shows no signs of chilling and bears evidence of crystallization as an open system. The variolitic structures in the inner component result from liquid immiscibility between droplets of acidic melt and basic host magma, the former originating as buchitic liquid caught up by the dyke magma at its contacts with mobilized country rock. Both components afford textural evidence of the immiscibility of a sulphide melt in the tholeiitic magma. The petrography and thermal behaviour of the inner dyke-member support its recognition as a probable former feeder to fissure eruption.

Platinum, palladium, gold, and iridium have been determined by radiochemical neutron-activation analysis in three lateritic profiles developed on serpentinized peridotite. In addition, a number of major, minor, and other trace elements have been estimated by conventional chemical, instrumental neutron-activation, and radiochemical methods. The fractionation of the elements as a result of the tropical weathering has been investigated as a function of depth. Each of the profiles L--Guatemala, BNC--New Caledonia, and BIP--Indonesia- has a lower decomposed serpentinite zone and upper zones enriched in iron nl oxides and hydroxides.

Hohmannite is a hydrated sulphate of ferric iron with the formula Fe2(SO4)2(OH)2.7H2O (Palache, Berman, and Frondel, 1951).

Figs. 1 and 2 illustrate the structure of hohmannite. The first shows a complex chain of Fe(O, H2O)6 octahedra and SO4 tetrahedra, which runs along the c axis; the second visualizes the water molecules and an hypothetical hydrogen-bonds system obtained on the basis of electrostatic and geometrical considerations.

Ferrocarpholite has been discovered at two localities in low-grade blueschists in the Diahot region, northern New Caledonia. In one occurrence (specimen 23503), ferrocarpholite was found in quartz veins associated with metamorphosed rhyolitic tufts, and at the other locality (23514) it occurs as a gangue mineral at Ao Mine associated with quartz, a variety of carbonates, and sulphide ores.