MINERALS 115 



locate them may take keen observation and much careful 

 searching. After selecting the most promising localities for work, 

 take out as many good specimens as time will permit. Set these 

 in a safe place, sort them over, and group them as to appearance 

 and mineral association. Try to get as many different mineral 

 associations as you can from each place. Do not pack the minerals 

 or make final selection until your prospecting for the day or 

 place has ended; then select only the most important. 



If there are old, abandoned mines and quarries available, first 

 visit the dumps and old ore piles. Broken up rock usually offers 

 the best collecting; generally it is best to avoid large blocks of 

 rock. Never enter an abandoned underground mine alone, unless 

 you have had previous mining experience and are equipped with 

 a good light. 



In areas of volcanic rocks search for those containing cavities. 

 Minerals often occur in these cavities. If the area is one of 

 granitic or coarse crystalline rocks, search for dikes or veins that 

 cut the rocks, as in these veins the minerals may be more coarsely 

 crystalline. Look along any open fractures or joints present. 



In limestones look for minerals which weather out differently 

 from the rest of the rock. Search for solution cavities, and 

 examine bedding planes and joints. Split shales and slates hori- 

 zontally along the bedding to recover material between the layers. 



Wherever two rocks of a different nature have a common 

 contact, examine this carefully for unusual minerals. 



Rivers and beaches are excellent places to get a preliminary 

 idea of the types of rocks existing toward the headwaters of 

 the drainage area to which they belong. Examine the gravels 

 and the nature of the fine sand. Valuable deposits such as gold,, 

 platinum, tin, and precious stones often exist in heavy sands. 



