swanton: aboriginal terms for brother and sister 31 



can be interpreted as representing an isomorphous mixture 

 of 85 per cent of magnesium borate with 15 per cent of ferrous 

 borate. In its various properties magnesioludwigite shows the 

 expected differences from those of the iron-richer ludwigite from 

 Hungary. The luster is duller, the color lighter, the pleochroism 

 and absorption weaker, and the translucency of the crushed 

 material is markedly greater. 



These various changes in properties are correlated with the 

 changes in chemical composition, and the existence of a definite 

 series from the ferrous-iron borate to the magnesium borate is 

 well shown by specimens of the mineral from Hungary, Montana, 

 and Utah. This correlation is being made and will be given 

 in full in the detailed paper now in preparation. 



The increased knowledge of the variation in chemical com- 

 position and corresponding variations in other properties makes 

 it necessary to recognize the two end members of the series of 

 the natural magnesium-iron borates. It is therefore proposed 

 to use the name ludwigite as a group name, similarly to the usage 

 of the terms mica and feldspar, and to introduce the two names 

 magnesioludwigite and ferroludwigite for the end members and 

 for those parts of the series in which the magnesium or the 

 ferrous-iron borate, respectively, predominates. 



Including the mineral pinakiolite in the group, the ludwigite 

 group comprises then the following minerals, the term lud- 

 wigite being usable for any member of the group until its exact 

 relation has been determined: 

 Group 



Ludwigite 

 Species 



Ferroludwigite, FeO.Fe 2 3 .3MgO.B 2 3 

 Magnesioludwigite, MgO.Fe 2 3 .3MgO.B 2 3 

 Pinakiolite, MnO.Mn 2 3 .3MgO.B 2 3 . 



ANTHROPOLOGY. — Significance of the terms for brother and 

 sister among primitive peoples. John R. Swanton, Bureau 

 of American Ethnology. 



It is well known that among tribes divided into clans or 

 gentes the terms for those relations for which we use "brother" 



