Raw gold, in its natural state, captivates with its unique presence, a stark contrast to the polished forms often seen in jewelry. It is the pure form of this precious metal, found directly within the Earth’s crust or in alluvial deposits. Understanding what raw gold looks like involves observing its distinct physical properties, which differentiate it from many other minerals.
Defining Raw Gold’s Appearance
Raw gold possesses a distinctive metallic luster, often described as buttery or greasy, reflecting light in a soft, non-sparkling manner. Its color is a rich, deep yellow that does not tarnish or fade upon exposure to air or water, remaining vibrant across all lighting conditions. Gold is soft and malleable, meaning it can be easily bent, flattened, or reshaped without breaking. It can deform under pressure, such as being scratched with a knife or even a copper penny, and is highly ductile, capable of being drawn into extremely thin wires.
Common Forms of Raw Gold
Raw gold appears in several forms, influenced by its geological origins:
Gold nuggets are irregular, rounded pieces smoothed by water, often found in streambeds. They are solid and dense.
Gold flakes are smaller, flat pieces often found alongside nuggets in placer deposits.
Gold dust consists of very fine particles, representing the smallest form.
Gold can also be found embedded within rock formations, such as quartz veins, appearing as streaks, specks, or wire-like structures.
Distinguishing Raw Gold from Look-Alikes
Many minerals can be mistaken for gold, but several simple tests can help differentiate them. Pyrite, an iron sulfide, is a common look-alike with a brassy yellow color and a metallic sheen that can appear glittery. Chalcopyrite, a copper iron sulfide, also exhibits a brassy to golden yellow color, sometimes with an iridescent tarnish. Mica, particularly biotite or phlogopite, can also deceive with its reflective, gold-like flakes.
Streak Test
A key differentiating factor is the streak test, which reveals the color of a mineral in powdered form. Real gold leaves a yellow or golden streak when rubbed across an unglazed porcelain plate. In contrast, pyrite produces a greenish-black to brownish-black streak, while chalcopyrite leaves a greenish-black streak. Mica, being translucent, typically leaves a white streak.
Hardness and Malleability
Hardness and malleability also provide clear distinctions. Gold is soft, with a Mohs hardness of 2.5 to 3, meaning it can be easily scratched by a copper penny or a knife; it is also highly malleable and will flatten or bend when struck or pressed. Pyrite, however, is much harder (Mohs hardness of 6 to 6.5) and will scratch glass or resist being scratched by a knife; it is brittle and will shatter or crumble rather than deform. Chalcopyrite has a Mohs hardness of 3.5 to 4, making it harder than gold but softer than pyrite, and it is also brittle. Mica flakes will typically break apart under pressure, unlike gold which will bend.
Density
Density is another crucial indicator. Gold is exceptionally dense, with a specific gravity of approximately 19.3, making even small pieces feel surprisingly heavy for their size. Pyrite has a specific gravity of about 5, making it significantly lighter than gold of comparable size. Chalcopyrite also has a lower density than gold, ranging from 4.1 to 4.3 g/cm³. This noticeable weight difference is often one of the most reliable field tests.
Factors Influencing Raw Gold’s Appearance
The appearance of raw gold can vary slightly depending on the presence of natural impurities or other metals alloyed within it. Gold found in nature is rarely 100% pure; it often forms natural alloys with other elements. The most common impurity is silver, which can lighten gold’s characteristic deep yellow color, giving it a paler or whitish-yellow tint if the silver content is high. Copper is another common alloy, which can impart a reddish or coppery hue to the gold. The geological environment and subsequent weathering processes can also affect the surface appearance of raw gold, though these variations are typically superficial and do not diminish the metal’s fundamental characteristics.