Almost any other kind of metal will dissolve in the acid. However, nitric acid will not affect iron pyrites or mica (fool's gold), but those are brittle and will not pass the hardness test. CAUTION: Nitric acid can be dangerous to work with.
Genuine gold will stand up to your attempt to conduct a nitric acid test at home. Make a tiny mark on the piece of gold to penetrate the surface. Drop a small amount of liquid nitric acid on that scratch and wait for a chemical reaction. Fake gold will immediately turn green where the acid is.
Hardness: Gold is much softer than pyrite. A good way to test whether or not a mineral is a piece of pyrite is to do a scratch test on a substance that is harder than gold but softer than pyrite, such as copper. While pyrite will leave a scratch on the copper, it's more valuable counterpart will not.
Pyrite has a cubic structure; gold does not. Take a magnet with you. Iron pyrite will stick to the magnet because of its high iron content; gold will not. You can also use a drop of nitric acid to test your specimen.
The acid test for gold is to rub the gold-colored item on black stone, which will leave an easily visible mark. The mark is tested by applying nitric acid, which dissolves the mark of any item that is not gold, stainless steel, zinc, tungsten, aluminum, platinum, or palladium.
Acid tests have a relatively high tolerance. In other words, they are a good rough estimator of gold using the Karat scale, and even then, you shouldn't rely on it to the decimal point. Simply put, acid testing isn't always the most accurate.
If your gold piece turns black or green when the vinegar is on it, or if it starts to smoke or fizzle at all when the vinegar touches it, it is most likely not real gold. If your gold piece does not change colors and does not fizzle or react to the vinegar in any way, it is probably real.
"Fool's gold" is a common nickname for pyrite. Pyrite received that nickname because it is worth virtually nothing, but has an appearance that "fools" people into believing that it is gold.
It is a lustrous mineral, meaning that it reflects light. When it is pulverized into a fine powder or dragged across a surface to create a streak, it appears greenish-black in color. This property of pyrite can be used to distinguish it from gold, which retains its yellow color even when pulverized or streaked.
During World War II it was mined to produce sulfuric acid, an industrial chemical. Today, it is used in car batteries, appliances, jewelry, and machinery. Although fool's gold can be a disappointing find, it is often discovered near sources of copper and gold .
In addition, actual gold will leave a golden yellow streak when scraped on a piece of unglazed porcelain. Pyrite and chalcopyrite will leave a dark green to black streak and the common micas will leave a white streak.
Perform a Streak Test
When rubbed against a streak plate (unglazed ceramic tile) minerals will leave a distinct color streak behind which can aid in the identification process. Gold leaves a distinct yellow streak, whereas pyrite leaves a rather ugly greenish-black streak.
The acid test (also known as the touchstone test) is the standard for almost all pawnshops and jewelers in the US, it is second to XRF testing (X-Ray Fluorescence testing) which is far more specialist and expensive. XRF machines can cost $20,000 or more, so you can understand why it's not all too common.
Nitric Acid is then applied to the mark. If it easily dissolves, the item is not Gold. If the mark remains, Aqua Regia (Nitric Acid and Hydrochloric Acid) is then applied. If mark is removed then this test proves the gold is genuine.
Place your jewelry on a table or hold it in your hand, pour some white vinegar on the metal directly (a dropper can also be used) if the metal of the jewelry changes its color, it is not pure gold and if it keeps shining then you have real gold in your hand.
(a) Pyrite is iron (II) sulfide whose chemical formula is F e S . It reacts with aqueous hydrochloric acid, H C l , via double-displacement reaction wherein these two compounds switch their ions to form aqueous iron (II) chloride, F e C l 2 , and gaseous dihydrogen sulfide, H 2 S .
Pyrite dissolution at temperatures higher than 45 °C and up to 85 °C was between 72% and 95% after 120 min leaching in 3 M HNO3. At nitric acid concentrations between 2.5 M and 4 M, HNO3 had a powerful oxidising ability, resulting in an ample pyrite dissolution of between 74% and 95%.
Pyrite is not easily scratched and will shatter like glass if struck by a hammer. In fact, if you take a piece of copper and scratch it with a piece of pyrite, it will a scratch on the copper. If you repeat the test with gold instead of pyrite, the gold will be scratched.
Three conventional processes for recovery of gold and silver from complex pyrite or arsenopyrite ores are roasting, pressure leaching (autoclaving) and bioleaching.
Pyrite is a special weakly magnetic mineral containing Fe(II). Its self-magnetization only by adjusting slurry temperature and pH value was able to enhance its magnetism, producing the so-called the magnetized pyrite, which was further used as magnetic seeds in the flotation of pyrite ore to promote flotation recovery.
Pyrite may float due to natural or self-induced hydrophobicity or collector-induced hydrophobicity. Its flotation can also be enhanced by the activation of copper or lead ions emanating from other minerals.