176 III. DIST. CHAR. Soil. 



The matrix is distinguished according to its for- 

 mation, substance, and parts. 

 * Formation. 



According to which the matrix is said to be 

 genuine, spurious, continued, distinct, &c. 



a. 156. A GENUINE MATRIX (M. genuina) is 

 formed from the mineral matter which first attached 

 itself to the external surface of the original, organic 

 body, 



b. 157. A SPURIOUS OR SUPPOSITITIOUS MATRIX 

 (M. supposititia) is formed from mineral mat- 

 ter which has taken place of that originally sur- 

 rounding the extraneous body. 



Obs. In many instances the true or genuine ma- 

 trix is removed, and its place and form assumed by 

 other matter. This is frequently the case with the 

 extraneous fossils of veins. 



Stones with a sparry or crystalline fracture, 

 and the metallic substances ( the iron ores excepted ) 

 rarely form any other than supposititious matrices. 



c. 158. A CONTINUED MATRIX ( M. coutinuata) 

 formed by a part of the seat ( 152) not distinct in 

 structure and substance from the seat. 



Obs. A continued matrix is mostly a true or ge- 

 nuine one Limestone strata are generally continued 

 matrices. 



d. 159. A DISTINCT MATRIX (M. distincta) dif- 

 fering in substance or structure from the scat A 

 distinct matrix may be 



