THE PYROXENE AND AMPHIBOLE GROUPS (NEPHRITOIDS) 45T 



between 3-5 and 3-6. It is only slightly translucent, and its liistic is feeble, but it is 

 susceptible of a moderately good polish. 



Rhodonite is sometimes erroneously referred to as manganese-spur. This is a car- 

 bonate of manganese, of which the mineralogical name is rhodochrosite ; it is of a pretty 

 rose-red colour, but is too soft to be worked for ornamental purposes. 



On account of its colour, which is somewhat similar to that of rhodonite, we may 

 here, in passing, briefly describe a mineral which belongs not to the ))yroxene but to the 

 mica group. 



LEPIDOLITE. 



The colour of this mineral is not a pure rose-red, but shows a tinge of blue or violet^ 

 and therefore inclines more to lilac. Lepidolite is a lithia-mica, a finely granular to 

 compact variety of which is found in some quantity at Rozena, in Moravia. It is some- 

 times fashioned into small ornamental articles of various kinds for the sake of displaying 

 its pretty lilac-red colour, but since the hardness is only 2, and it can be scratc-hed with the 

 finger-nail, it is useless for other purposes. 



NEPHRITE. JADEITE. CHLOROMELANITE. 



These three minerals are sometimes collectively referred to as nephritoids. They were- 

 used as precious stones in prehistoric times, and objects of various kinds fashioned out of 

 them have been found in Europe among the remains of the Stone Age. At the present 

 time their use for ornamental purposes is limited and mainly confined to a few countries 

 outside Europe. 



The first mentioned of these minerals, nephrite, belongs to the amphibole or 

 hornblende group, and the other two, jadeite and chloromelanite, which only differ in 

 unessential characters, belong to the pyroxene or augite group. In spite of the fact that 

 these three minerals are classified mineralogically into two different, though closely related 

 groups, they resemble each other very closely in external appearance, in certain other of 

 their characters, and in the purposes to which they are applied. Structurally they may be 

 described as being very finely fibrous to compact aggregates, the individual constituents of 

 which are only recognisable when thin sections of the mineral are examined under the 

 microscope. The substance, especially when polished, appears in each case, as far as can be 

 made out with the naked eye, perfectly homogeneous, and the appearance is rather such 

 as one associates with fused material. When thin sections are observed under a high 

 magnification, however, it is seen that the substance in every case is built up of very 

 numerous fibres matted together. Although the hardness of these minerals is not very 

 considerable, being between 6 and 7 on the scale, yet, on account of their fibrous structure, 

 they are exceptionally tough and more difficult to fracture than any other substances in the 

 minei'al world ; this character being specially conspicuous in nephrite. Because of their 

 toughness, and also because of their pretty appearance, the nephritoids, even in prehistoric 

 times, were used in the fashioning of idols, ornamental objects, and tools, such as axes 

 and chisels. Such objects are now found in Europe and other countries, in ancient lake- 

 dwellings, graves, &c., and also lying loosely in the surface soil. 



Until comparatively recently, the three minerals under consideration were found both 

 in Europe and America only in the worked condition, and the occurrence of rough material 



