Gold 307 



less, are thought to have been so slow that they attained their 

 effects by persisting through a vast period of time. The Mother 

 Lode fissuring may logically be regarded as a very late mani- 

 festation of these stresses after their intensity had become 

 greatly reduced. Instead of effecting further folding of the 

 rocks enough relief of the stresses was afforded by fissuring and 

 slight movement localized in the zone of weak rocks that 

 became the Mother Lode. 



"The position of that zone of weakness, and hence the gen- 

 eral course of the Mother Lode seems to have been determined 

 by the winding course of the Mariposa formation that pre- 

 viously had been infolded within the Calaveras. The mines 

 of the lode definitely follow this course of the Mariposa rocks. 

 The width of the Mariposa exposed along the lode is not great, 

 averaging less than a mile, and through long distances not half 

 that width, yet the number of mines in the Mariposa or very 

 nearly adjacent to its contacts exceeds the number of all other 

 mines." 



What is known as the Gold Belt includes other gold-bearing 

 regions both north and south of the Mother Lode. It extends 

 along the lower western slope of the Sierra Nevada from 

 Plumas County on the north to eastern Mariposa County on 

 the south, and is bounded on the west by the San Joaquin and 

 Sacramento valleys. The area embraces about 9,000 square 

 miles. At the northern limits of the belt the gold deposits are 

 scattered over nearly the whole width of the range. At the 

 south the productive region narrows to a strip which extends 

 for some miles south from the main belt. 



Some Questions Not Answered 



The question naturally arises why gold in such unusual 

 quantities should occur in this particular region. What is the 

 Mother Lode? This can be definitely answered. Why is the 

 Mother Lode; why gold came to exist in a great aggregate of 

 mineral veins along a somewhat irregular belt on the lower 



