The prospect of discovering gold in its natural state within rock captivates many. Accurately identifying real gold can be challenging due to its visual similarities with several other common minerals. Understanding the distinct characteristics of genuine gold, and how it differs from its look-alikes, is crucial for anyone hoping to discern a true discovery.
Key Visual Traits of Real Gold
Real gold, when found embedded in rock, often displays a distinctive bright to buttery yellow color. This metallic hue is consistent throughout the material, unlike other minerals that show varying shades or brassier tones. It possesses a high metallic luster, meaning it reflects light strongly and can appear shiny even in shaded conditions. Its shine is often described as a soft glow rather than a harsh, mirror-like reflection.
A defining characteristic of natural gold is its exceptional malleability, which means it can be flattened or bent without breaking. If pressed with a tool like a knife, real gold will dent or scratch, whereas other minerals would likely crumble or resist the pressure. In rock, gold typically occurs in irregular shapes like flakes, grains, or small rounded masses, often without sharp edges or crystalline structures. It rarely forms well-defined crystals, and if present, they lack the parallel lines or striations often seen on other metallic minerals. Gold is frequently found within quartz veins, appearing as small specks or thin veins within the white or translucent quartz.
Common Minerals Mistaken for Gold
Pyrite, commonly known as “fool’s gold,” is often mistaken for gold. It has a brassy yellow color and metallic luster, but often forms distinct cubic or octahedral crystals with visible striations, absent in true gold. Unlike gold, pyrite is brittle and shatters when struck, rather than deforming. Its hardness is significantly greater than gold, making it resistant to scratching with a knife.
Mica, like muscovite or biotite, can also be mistaken for gold due to its shiny, flaky appearance. These minerals occur in thin, flexible sheets that reflect light, resembling gold. However, mica flakes are lighter than gold and lack a true metallic luster, appearing more transparent or translucent. When scratched, mica will easily flake or crumble. Chalcopyrite, a copper iron sulfide, also has a golden hue but typically presents with a greenish tint and is softer and lighter than gold.
Simple Field Tests for Identification
Several field tests can help distinguish real gold from other minerals. The streak test involves rubbing the mineral across an unglazed ceramic plate. Real gold leaves a metallic yellow streak, while pyrite produces a greenish-black streak, and mica leaves a white streak.
Another test involves assessing malleability and hardness. Gold is soft and can be easily scratched or dented with a knife or copper penny. In contrast, pyrite resists scratching or shatters, while mica simply flakes apart.
The density test is highly effective, as gold is exceptionally heavy for its size, with a specific gravity of around 19.3 grams per cubic centimeter. A gold-bearing rock will feel noticeably heavier than a similarly sized piece of ordinary rock or minerals like pyrite, which are less dense.
Finally, gold is not magnetic. If a magnet attracts the shiny material, it is not gold.