YELLOW GOLD

Gold, being so soft and mechanically tolerant to pliers, pincers, hammers, etc., can adopt any desired shape with great detail. The metal is rarely used in its pure state, except when used for plating (gold baths).

Traditional gold alloys are measured in karats (expressed as "k"), based on 24 parts for pure gold. The most famous grades are 22k, 18k, 14k, and 10k or 9k, depending on the region. As the percentage of gold decreases, so does the quality of the jewel and, consequently, its price. Very rarely is the gold content expressed as a percentage, as when karats are not used to assess purity, thousandths are used (which is the usual measure for Silver and Platinum).

To find the equivalences, simply divide the jewel's karats by 24 parts and then multiply by 100, which will give you the percentage of pure gold.

For example, for a 14k gold ring, you have:

14/24 = 0.5833<br>0.5833 × 100 = 58.33% pure gold by mass

It's easy, right?

To determine the specific amount of gold contained in a piece (whether or not it's personal jewelry), multiply the result of the division directly by the weight of the piece, instead of multiplying by 100.

For example, for an 18k gold ring weighing 12 grams, you have:

18/24 = 0.75 ergo,<br>0.75 × 12 grams = 9 grams of pure gold by mass

I believe even a preschooler could do it.

The highest gold alloy with a sufficiently important use to be noteworthy is 22k, and its primary use is for dental implants or the "caps" that some people like to put on their teeth, even as a lining for a healthy tooth for purely aesthetic reasons.

The most important gold alloys for rings, chains, bracelets, watches, etc., are 18k for Europe and South America and 14k for North America. 18k gold is called "high gold" or "hallmark gold" (oro de ley) and is the highest grade typically used because it contains sufficient quantities of Copper, Silver (and more recently, Zinc, Aluminum, and even Titanium or other rare elements) that increase its hardness. The percentage of gold is NOT reduced to make the jewel cheaper, as many people think, but because pure gold is too soft to be used without fear of deforming it. Even the slightest impact would dent or scratch it (Mohs hardness = 2.5).

Although both Copper and Silver are soft on their own, when mixed, they result in a tougher gold. Depending on the percentages of Silver or Copper, the final color of the alloy acquires a different shade.

Silver is unable to completely remove gold's golden color, even if it were saturated to more than 50% (as is the case with the alloy known as Electrum used by the Romans), but its effects are noticeable as the golden color of pure gold acquires a "greenish" hue due to excessive Silver. Copper hardens gold more and, if anything, improves its color (some people are particularly attracted to "rose gold"), but being a "base" (non-noble) metal, it is added in small doses. Classic, good-quality yellow gold is a typical mixture of 75 parts Gold, 20 parts Silver, and 15 parts Copper, although the quantities may vary. Remember that not all jewelers are honest (not even big brands, how could artisans be?) and sometimes they lower the gold content as long as they can make it appear higher than it actually is.

Currently, Zinc is added to the mixture as it improves the mechanical properties and the resulting luster, but personally, I am wary as Zinc and Copper themselves form a golden color (that of Brass) that could disguise the authentic gold.

If you are unsure, buy gold from someone whose reputation is infallible or, simply, don't buy gold. That's all I can tell you.

Currently, and given that gold is increasingly scarce, a thousand tricks and tests have been made to achieve results similar to authentic gold with varying degrees of success. The problem is that as the human population increases and the average citizen's purchasing power in developed countries also balances out, with every wedding band used for a wedding (think millions of couples marry worldwide each year), gold becomes more affordable, so the price systematically increases, and even when you pay a huge amount, you might still get ripped off.

These are conjectures, of course; I'm trying to warn you. The vast majority of jewelers are honest, but it happens that when one tries to be too clever, the whole trade ends up paying for it.

As the gold content decreases, the combinations (or "alloys") of metals with which it is combined to make the final alloy proper become increasingly varied depending on the artisan; there is no standard or regulatory consensus as in steel alloys, whose chemical composition is controlled by, among other bodies, AISI or SAE, which despite being old seem like newborns when you compare the history of metallurgy to that of gold jewelry. The "formulas" with which gold, and to a lesser extent silver, metal mixtures or "alloys" are made are ancestral and have been passed from father to son for millennia (literally). Each "school" follows its procedure, and ultimately each jeweler chooses the combination that gives them the best result. I'm not saying it's wrong or right, I'm just informing you.

The 14k grade is the most popular in the United States and is considered "medium gold," although the best jewelers have catalogs ranging from 18k to 9k. Lower grades are preferred for making "white gold" as they allow the addition of white metals such as Palladium, Silver, Nickel, Manganese, Zinc, and even Tin or Bismuth. Palladium and Silver are preferred because both are noble (and also justify the price of the alloy), although the results obtained with Nickel are better, this metal causes allergies in some people and therefore is either used in small doses or not at all.

Manganese whitens as well as or better than Nickel but achieves a more opaque finish, if possible, and is the most reactive metal among those that can be chosen to fulfill this function.

Gold is not easy to whiten; very high percentages of other metals are needed to counteract the characteristic golden tint of the king metal, and even when this is achieved, neither the color nor the luster is entirely attractive, so they are covered with a layer of Rhodium.