MOLDAVITE 44.9 



MOLDAVITE. 



Moldavite is a glassy substance, the origin of which has not yet been definitely 

 determined. It is known as bottle-stone, or as pseudo-chrysolite, on account of its 

 resemblance to green bottle-glass and to green olivine (chrysolite), the resemblance being so 

 close that faceted specimens of moldavite can only be distinguished from the substances 

 mentioned by careful examination. To lapidaries the mineral is usually known as water- 

 chrysolite. 



Moldavite, like obsidian, has the chemical composition and physical characters of a 

 glass. It can only be distinguished from obsidian with the naked eye by its perfect 

 transparency and its green colour. The colour is never very deep, varying between leek- 

 green and olive-green ; specimens of a light brown colour are sometimes met with, but are 

 rarely cut as gems. The mineral is amorphous and therefore optically singly refracting and 

 not dichroic ; it is brittle, breaks into sharp angular fragments, possesses a perfect conchoidal 

 fracture and a strong vitreous lustre, all of which features it has in common with obsidian. 

 Its hardness is about 5i and its specific gravity is 2"36, rather less than is usually the case 

 with obsidian. 



Although, externally, moldavite so closely resembles a piece of green bottle-glass or 

 of trans))arent green obsidian, internally there are well-defined differences. Under the 

 microscope moldavite is seen to contain vast numbers of minute air bubbles such as are seen 

 neither in glass nor in obsidian, and the microscopic crystals always present in obsidian are 

 absent in moldavite. Moreover, chemical analysis shows that the composition of moldavite 

 is variable like obsidian, but that the substance contains more silica than is present either 

 in artificial glass or in obsidian. Furthermore, moldavite contains no potash and very 

 much less lime than is present in glass. The following is an analysis by C. von John of a 

 specimen of moldavite from Trebitsch in Moravia : 



Per cent. 



Silica (SiOg) 81-21 



Alumina (AlgOj) , . .... 10'23 



Ferrous oxide (FeO) 2-45 



Lime (CaO) 2'10 



Magnesia (MgO) 1-08 



SodaCNajO) 2-43 



Loss on ignition 004 



99-54 



The percentage of silica present may be as low as 76 and as high as 83. Moldavite 

 fuses before the blowpipe only with great difficulty, and the fused mass after cooling is 

 perfectly clear, so that in this respect also the mineral differs from obsidian and from glass. 



It will be seen from the foregoing that though moldavite has many characters in 

 common with green glass and obsidian, yet that there are important differences between 

 moldavite and the two latter substances. It is, therefore, still uncertain whether moldavite 

 is to be regarded as a natural glassy lava or as an artificial product. At the localities in 

 Bohemia and Moravia, where the substance is found, there has flourished since ancient times 

 a glass-making industry, and it is thus possible and even probable that moldavite is an 

 artificial glass. Professor Suess has recently advanced the suggestion that moldavites are of 

 cosmic origin and that they represent a hitherto unrecognised type of meteoric stone. He 

 maintains that the peculiar surface markings cannot have been produced by attrition iji 



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