Gold ore is a naturally occurring rock that contains gold in concentrations high enough to make it economically viable to extract. The gold within the ore is often found as tiny particles or microscopic flecks mixed with other minerals such as quartz, sulfides, or other metals like silver and copper.

*Types of Gold Ore:*

1. *Lode Deposits:* These are gold ores found in veins or within rock formations, often associated with quartz and sulfide minerals. This is the most common type of gold deposit mined today.

2. *Placer Deposits:* These are deposits where gold has eroded from its original rock and settled in riverbeds, streams, or beach sands. Gold is often found as flakes, nuggets, or dust in these settings.

3. *Refractory Gold Ore:* This type of ore contains gold that is locked within minerals, making it difficult to extract using conventional methods. Special processing, such as bio-oxidation or roasting, is often required.

*Extraction Process:*

To extract gold from the ore, miners use various methods:
*Crushing and Milling:* The ore is crushed and ground to liberate the gold particles.
*Gravity Concentration:* Gold is separated from other minerals based on its density, often using a process like panning or sluicing.
*Cyanidation:* The most common method, where gold is dissolved using a cyanide solution, and then recovered from the solution by precipitation.
*Smelting:* The concentrated gold is heated to high temperatures to melt and separate it from other impurities.

The quality of the gold ore is measured by its grade, which indicates the amount of gold present per tonne of ore. High-grade ores contain more gold, making them more valuable.