44 SCIENCE PROGRESS 



In a paper on the changes in constitution which occur when 

 clay is transformed into shales, slates and phyllites, A. Brammall 

 {Miner. Mag., 19, 211, 1921) carries to a further stage the work 

 done by Hutchings thirty years ago. By means of a series of 

 analyses, the recrystallisation of the rock material as sericite, 

 chlorite and quartz is traced and the development of the 

 accessory minerals, such as titanite, is accounted for on the 

 basis of the oxides set free during these changes. The origin 

 and course of crystallisation of certain schists from Macedonia 

 is discussed by O. H. Erdmannsdoerffer {Zeit. Kryst., 56, 419, 

 1921). 



The investigation of Japanese kaolinite by means of heating 

 and cooling curves is described by S. Satoh (Journ. Anier. Cer. 

 Soc, 4, 182, 1 921). Several changes, both exo- and endo- 

 thermic in character, have been noted, in addition to those 

 previously described. A differential method of examination 

 was used, but as the supposed inert substance adopted was 

 quartz, the results are vitiated by the changes which occur in 

 the latter during heating and cooling. 



I. Bellucci and L. Grassi {Gazz. chim. Ital., 49, 232, 1920) 

 have described crystals of fluorapatite containing over 5 per 

 cent, of rare earth oxides, mainly cerium. The occurrence of 

 the scandium mineral, thortveitite, in Madagascar is noted by 

 A. Lacroix [Compt. Rend., 171, 421, 1920). In the magnesite 

 deposit at Galgenberge in Silesia, L. Mahlen [Zeit. prakt. Geol., 

 28, 155, 1920) ascribes the formation of the mineral to the 

 leaching of magnesia from serpentine, followed by enrichment 

 through colloidal solutions at considerable depths and ultimately 

 by crystallisation. The amount of serpentine diminishes as 

 the depth increases. 



The metasomatic formation of breunnerite from peridotite 

 through the agency of post-volcanic emanations such as carbon 

 dioxide and water, is described by W. Hammer [Cent. Min., 

 385, 1921). 



R. Scharizer [Zeit. Kryst., 56, 353, 192 1) continues his work 

 on the constitution and origin of the natural sulphates of iron. 

 In this paper the mineral rhomboclase, Fe(OH) (H 804)23 HgO, is 

 considered and details are given concerning its crystallographic 

 properties and behaviour on hydrolysis. The corresponding 

 anhydrous salt has also been prepared and the conditions of 

 its formation examined. 



The natural hydrates of ferric oxides are classified by K. 

 Willmann {Cent. Min., 673, 1921) into two groups, colloidal 

 and crystalline hydrates. The former are regarded as forming 

 a continuous series, the water content varying from 5 to 25 

 per cent. In the latter, three definite minerals are recognised, 

 two of these being polymorphic modifications of the mono- 



