8 SOILS AND FERTILIZERS 



7. In what way were igneous rocks formed ? Sedimentary 

 rocks ? Metamorphic rocks ? Name examples of each. 



8. Name a mineral containing potash, a mineral containing lime, 

 a mineral containing magnesia, a mineral containing phosphoric acid, 

 a mineral containing sulfur, a mineral containing iron. 



LABORATORY EXERCISES 



The following exercises are designed to suggest possible experi- 

 ments and demonstrations that may be carried out in connection 

 with the various chapters. Some may be performed by the student 

 if adequate facilities are at hand, some are only possible as demon- 

 strations, while others are field studies and depend on local condi- 

 tions. Enough suggestions are made with each chapter to give the 

 teacher a range of choice according to his conditions and facilities. 

 It is not considered possible or advisable that all the experiments 

 and demonstrations listed be carried out. 



Exercise I. — Study of soil-forming minerals. (The teacher will 

 find an elementary text in mineralogy of great aid in this experi- 

 ment.) 



Materials. — Small specimens of quartz, potash-feldspar, mica, 

 calcite, apatite, gypsum and hematite. Also a piece of a glass, a 

 knife, dilute muriatic acid, a hand-lens and flame (gas or alcohol). 



Procedure. — Study the specimens according to the following 

 outline, with a view to identifying the minerals unlabeled. Use 

 hand lens where possible 



Hardness. — Determine hardness by the following scale. 



Hardness Mineral 



Scratched by finger nail GypsumN >Mica 



Cut by knife Calcite / 



Scratched with difficulty with knife . . Apatite 



Scratches glass Feldspar — Hematite 



Scratches glass very easily Quartz 



Color. — Observe color and luster of the various specimens and 

 determine if it is characteristic and useful in identifying the mineral. 



Cleavage and fracture. — Do specimens split easily in certain direc- 

 tions or do they fracture ? What effect do these characters have 

 upon the appearance of the mineral ? 



Form. — Do the specimens seem to have any crystal form that 

 is characteristic and useful in identification ? 



