Mineral Preservatives in the Wood of Stradivari and Guarneri

Following the futile efforts of generations to reach the high standard of excellence achieved by the luthiers in Cremona, Italy, by variations of design and plate tuning, current interest is being focused on differences in material properties. The long-standing question whether the wood of Stradivari and Guarneri were treated with wood preservative materials could be answered only by the examination of wood specimens from the precious antique instruments. In a recent communication (Nature, 2006), we reported about the degradation of the wood polymers in instruments of Stradivari and Guarneri, which could be explained only by chemical manipulations, possibly by preservatives. The aim of the current work was to identify the minerals from the small samples of the maple wood which were available to us from the antique instruments. The ashes of wood from one violin and one cello by Stradivari, two violins by Guarneri, one viola by H. Jay, one violin by Gand-Bernardel were analyzed and compared with a variety of commercial tone woods. The methods of analysis were the following: back-scattered electron imaging, X-ray fluorescence maps for individual elements, wave-length dispersive spectroscopy, energy dispersive X-ray spectroscopy and quantitative microprobe analysis. All four Cremonese instruments showed the unmistakable signs of chemical treatments in the form of chemicals which are not present in natural woods, such as BaSO4, CaF2, borate, and ZrSiO4. In addition to these, there were also changes in the common wood minerals. Statistical evaluation of 12 minerals by discriminant analysis revealed: a. a difference among all four Cremona instruments, b. the difference of the Cremonese instruments from the French and English antiques, and c. only the Cremonese instruments differed from all commercial woods. These findings may provide the answer why all attempts to recreate the Stradivarius from natural wood have failed. There are many obvious implications with regard to how the green tone wood should be treated, which chould lead to changes in the practice of violin-making. This research should inspire others to analyze more antique violins for their chemical contents

Partial melting and melt migration in the acapulcoite-lodranite parent body.

We review petrologic evidence that the acapulcoites and lodranites formed by < 1 vol% to probably 20 vol% whole rock partial melting of a chondritic precursor material. At low degrees of partial melting, only Fe,Ni---FeS cotectic melting occurred. Migration distances for partial melts were short, resulting in the formation of acapulcoites with essentially chondritic troilite and plagioclase contents, but achondritic textures. At high degrees of partial melting, both Fe,Ni---FeS and basaltic (plagioclase-pyroxene) partial melts formed, and the melts may have migrated out of the source rock. The partial melt residues, which are more or less depleted in Fe,Ni---FeS and plagioclase, are the lodranites. Melt migration was complex: most acapulcoites, which experienced relatively low degrees of partial melting, lost little if any of the partial melt. One acapulcoite, LEW 86220, represents a unique case in which Fe,Ni---FeS and basaltic partial melts appear to have migrated from a lodranite source region into a cooler acapulcoite region, where they were trapped. In cases of the relatively high degrees of partial melting experienced by lodranites, melts may have been partly, selectively, or totally removed from the rocks, and Fe,Ni---FeS and/or basaltic partial melts may have been removed to different degrees and may, in fact, have been trapped on occasion in greater than chondritic proportions. We model vein and dike formation and melt migration by calculating the excess pressures and vein and dike sizes for varying degrees of partial melting. Our calculations are broadly consistent with observations, indicating that melt migration is inefficient at low degrees of partial melting and extremely efficient at high degrees of partial melting. Although the size of the acapulcoite-lodranite parent body and the volatile contents of the chondritic precursor rocks are poorly constrained, the lack of basaltic rocks in the world's meteorite collections complementary to the lodranites suggests that basaltic partial melts may have been accelerated off the body by explosive volcanism of the type envisioned by Wilson and Keil (1991) and ejected into space. The diversity of rocks from the acapulcoite-lodranite parent body may provide a basis for better understanding the diverse range of spectral subtypes recognized among the S-type asteroids