Simplify the following text for a Grade 5 native English-speaking person.
Original: The bushrangers ' heyday was the Gold Rush years of the 1850s and 1860s as the discovery of gold gave bushrangers access to great wealth that was portable and easily converted to cash .
Simplified: The bushrangers were busiest during the Gold Rush years of the 1850s and 1860s . Gold can be easily carried and also it can easily be turned into cash .