T45, 46] SILICIFICATION — QUARTZ CRYSTALS. 25 



chalcedony (the usual material of silicified palm wood), through white hovnstone 

 to a soft fibrous mass resembling asbestos, which furnishes elegant objects for, 

 the microscope with the least possible trouble — the cells being thus separated, 

 though perfectly preserved. The asbestiform varieties are most frequent in S. 

 Hinds county, near the Mississippi Springs ; soft grayish hornstone is the 

 common material elsewhere. 



45. Not unfrequently, cavities occurring inside of silicified trunks, are found 

 studded with small, but very perfect crystals of smoky quartz. Some beautiful 

 specimens of this kind, from a large trunk, and with crystals of unusual size (}£ 

 to % inch in length) found on Lime Kiln Creek, have lately been presented by 

 the Rev. Mr. E. Fontaine, of Battle Springs, Hinds county. 



In this case, the external form of the trunk, as well as the outlines of its 



woody structure, are still distinctly recognizable on portions of the specimen, 



though crystallization has destroyed the detail. Crystals precisely similar to 



those just mentioned, but attached to a siliceous mass without any apparent 



structure, were found in S. Ocktibbeha county, a few miles S. of Whitefield, ou 



S. 21, T. 17, R. 12 E., near Mr. Dodson's place ; and the unusual character of, 



the specimens induced me to proceed to the spot for a special examination. The 



deposit is found on a low ridge, and has been traced for a mile and a half in a S. 



W. and S. direction, while (being confined to this single ridge) its width is 



inconsiderable — not more, perhaps, than twenty yards. It is a stratum 12 to 18 



inches thick (lying 2 to 3 feet below the nearly level surface), of a white siliceous 



rock, both the upper and lower surface of which is studded with crystals of 



smoky quartz, ^4 to % inch in length. The solid portions of the rock so closely 



resemble silicified wood, that an isolated fragment would be unhesitatingly 



referred to such origin ; it forms, however, as has been said, a level stratum of 



some extent, and there is very little curvature of the layers to be traced, even 



in large blocks. In the interior of the mass, there are many irregular 



drusy cavities, lined with numerous successive bands of siliceous mass and also 



studded with radiating crystals ; some of the solid portions themselves, in fact? 



are mere conglomerates of crystals, of a bluish tint. Their form is the hexagonal 



prism, in which both sets of planes are very evenly developed, while usually 



the terminal rhombohedrons are very unequally developed, so that one of them is 

 often entirely suppressed. 



The sand overlying this deposit bears all the characters of the Orange Sand 

 formation ; underlying it, however, there are sharp sands containing large scales of 

 mica, such as are but rarely seen among the Orange Sand materials, and greatly 

 resembling those accompanying the lignitic strata of the region. The nature of 

 the deposit itself, however, can leave little doubt that it is nothing more than a 

 bed of lignite which has undergone a process similar to that which has effected 

 the silicification of the uncompressed trunks commonly occurring. Fragments 

 of silicified wood are very common in the same neighborhood ; and lignite 

 beds are abundant in the adjoining portions of Ocktibbeha and Winston. 



46. I ought to mention, in connection with the subject of silicification, the 

 peculiar structure exhibited at times by certain cherty varieties of the hard 



