Gold and Silver occur natively here and there but much more commonly they occur with Sulfides and Tellurides. In order to separate the Gold and Silver from say a sulfide ore one of the methods used is known as Roasting. The process involves heating up the ores with certain salts in order to burn off the sulfides allowing you to recover the precious metals. There are many different charges and salts you may need to use depending on whether the ore is a Gold Telluride, A Gold-Silver Telluride, or a Copper-Silver Sulfide etc. This book discusses the different temperatures and mixtures that you need based on the type of ore you roasting. These methods are still used today in a lot of process plants. Once the ore is roasted the Gold and Silver can be recovered more easily by leaching and precipitation or by gravity methods which are all discussed in this book. Long out of print this book is now available again from Miningbooks.com.