The physical characteristics of gold are easily discerned with the naked eye. It should be a bright yellow color and weigh a considerable amount.
Gold does not oxidize, making it extremely durable and its color unchanging over time. Furthermore, it is unaffected by heat, air, humidity, or most chemicals, as it can only be dissolved in chlorine water, a mixture of potassium cyanide and water, or aqua regia. Gold only reacts when in contact with chlorine and bromine.

Gold is a rare and noble precious metal, known since Antiquity for its beauty, malleability and durability. It is a chemical element identified by the symbol Au, derived from the Latin word aurum, meaning "the shining one."

Physically, it is distinguished by its intense yellow colour and characteristic lustre, as well as its notable weight to the touch, owing to its high density (19.3 g/cm³). Gold does not oxidise or rust, preserving its natural brilliance across generations.

It is resistant to air, moisture and the vast majority of chemical products, making it one of the most stable and enduring metals on earth. It reacts only under very specific conditions — such as contact with aqua regia (a mixture of strong acids) or potassium cyanide — processes used in laboratory and refining industry settings.

These properties make gold a metal of significant economic value, widely used in jewellery, investment, electronics and even medicine.

In Portugal, the term ouro de lei ("legal gold" or "hallmarked gold") refers to gold whose purity has been legally recognised and certified by the Portuguese National Mint and Official Hallmarking Authority (INCM). Jewellery is manufactured using metal alloys — gold mixed with other metals such as copper, silver or palladium — to increase durability and adjust the colour tone.

The degree of purity is indicated by the fineness (also referred to as the millesimal fineness) — which represents the quantity of pure gold present in one thousand parts of the alloy. For example, the most traditional Portuguese hallmarked gold has a fineness of 800 parts per thousand (19.2 carats), meaning that 80% of the alloy is pure gold and the remaining 20% consists of other metals.

Every piece legally sold on the market must carry two mandatory marks:

• Maker's mark — identifies the manufacturer or goldsmith;
• Assay mark (INCM) — officially certifies the purity of the metal.

Ouro de lei does not simply mean that the piece is genuine gold — it means that it complies with Portuguese law and has been certified by the Portuguese National Mint and Official Hallmarking Authority (INCM).

Portuguese gold is recognised worldwide for its exceptional quality and purity. The most traditional fineness in Portugal is 19.2 carats (800‰), also known as "Portuguese gold." However, national legislation permits the production and sale of pieces in a range of fineness standards:

• 9 carat (375‰) — contains 37.5% pure gold;
• 14 carat (585‰) — contains 58.5% pure gold;
• 18 carat (750‰) — contains 75% pure gold;
• 19.2 carat (800‰) — contains 80% pure gold (traditional in Portugal);
• 22 carat (916‰) — contains 91.6% pure gold;
• 24 carat (999‰) — pure gold, used primarily in investment bars and coins.

Portuguese 19.2ct gold is so distinctive that it is frequently referenced internationally as one of the most prestigious gold standards, prized for its warm tone and the perfect balance between purity and durability.

The carat (ct) indicates the purity of gold, not its weight. Pure gold is considered to be 24 carats (24 parts gold in 24 parts alloy). As pure gold is too malleable for most practical uses, it is mixed with other metals (silver, copper, palladium, etc.) to achieve greater strength and rigidity.

This standard applies to all gold pieces. The higher the carat, the more valuable and costly the piece — and the greater its durability in terms of retaining its original brilliance and colour. Gold jewellery articles carry the following hallmarked fineness standards:

• 19.2ct (carats) or 800‰ (millesimal fineness) — composed of a minimum of 80% pure gold, with the remainder consisting of other metals in the alloy. This fineness corresponds to what is known as "Portuguese Gold."
• 18ct (carats) or 750‰ (millesimal fineness) — composed of a minimum of 75% pure gold, with the remainder consisting of other metals in the alloy.
• 14ct (carats) or 585‰ (millesimal fineness) — composed of a minimum of 58.5% pure gold, with the remainder consisting of other metals in the alloy.
• 9ct (carats) or 375‰ (millesimal fineness) — composed of a minimum of 37.5% pure gold, with the remainder consisting of other metals in the alloy.

Gold bars correspond to 24ct (carats) or 999‰ (millesimal fineness) gold — that is, gold not alloyed with any other metals.

Less common, but also permitted under Portuguese legislation, is 22ct (carats) or 916‰ gold, which corresponds to a minimum of 91.6% pure gold, with the remainder consisting of other metals in the alloy.

"All that glitters is not gold", as the saying goes — and it is true. Distinguishing genuine gold from imitations requires careful observation and, ideally, professional assessment. That said, there are several signs and tests that can help identify authenticity:

1. Look for hallmarks
Check whether the piece displays engraved symbols indicating its fineness (e.g. 375, 585, 750, 800, 916, 999). These numbers indicate the gold content and are generally accompanied by the INCM assay mark. Older pieces may have worn hallmarks — which does not necessarily mean they are not genuine.

2. The magnet test
Gold is non-magnetic and should not be attracted to a magnet. If the piece is strongly pulled towards it, it is not genuine gold. However, the absence of a reaction is not conclusive proof of authenticity, as some non-magnetic metals are also used in counterfeits.

3. The density test
Gold is one of the densest metals on earth (approximately 19.3 g/ml). A genuine gold piece will feel noticeably heavier than a fake of the same size. This test requires precision scales and a volume measurement tool, and is therefore typically carried out by professional appraisers.

4. The ceramic test
When rubbed against an unglazed ceramic surface:

• A gold streak → genuine gold;
• A black streak → base metal.

⚠️ This method may scratch the piece — not recommended for jewellery with sentimental value.

5. The nitric acid test
Genuine gold does not react to nitric acid, whereas base metals oxidise and change colour. This test must be carried out in a controlled environment by qualified professionals, as nitric acid is highly corrosive.

6. Professional appraisal
The safest and most accurate method is to take the piece to official appraisers certified by the Portuguese National Mint and Official Hallmarking Authority (INCM). At Loja do Ouro, we offer a free appraisal service carried out by licensed experts, using appropriate analytical instruments and chemical testing.

Weight, density, colour and hallmarks can all help identify gold — but only a certified appraiser can confirm authenticity with complete certainty.

The value of gold is determined by its international spot price, which fluctuates daily in line with financial markets. The global benchmark is set by the London Bullion Market Association (LBMA), where the gold price is fixed twice daily — in the morning and afternoon — in US dollars per troy ounce (31.103 g).

In Portugal, the price is converted to euros per gram and adjusted according to:

• The fineness (carat) of the gold being assessed;
• The international spot price on the day;
• The euro/dollar exchange rate.

You can consult the daily gold price table here.

The value of gold per gram changes every day, in line with the international spot price. The price you receive when selling your gold depends on:

• The carat (fineness) — 24ct gold is worth more than 19.2ct or 18ct gold;
• The total weight in grams;
• The spot price in effect at the time of appraisal.

You can consult the daily gold price table here.

The value of a gold bar (ingot) depends on three factors:

1. Weight — the most common sizes are 1g, 5g, 10g, 20g, 50g, 100g and 1kg;
2. Purity — typically 999‰ (24 carat);
3. The daily LBMA spot price.

Gold bars are currently among the most attractive investment products available — both due to the rapid and sustained appreciation of their value on international financial markets, and their ease of conversion into liquid assets. Each bar carries a unique serial number, the refiner's logo and a purity seal, guaranteeing authenticity.

You can consult the daily gold price table here.

If you are looking to sell some pieces of second-hand gold, the big question is always: how much is it worth? Gold prices tend to rise when the economy is stagnant or when there are concerns about inflation. Whether it is gold rings, gold earrings, necklaces or gold chains — selling the gold you no longer wear is an easy way to put extra money in your pocket.

First and foremost, it is necessary to determine the purity of the gold, whether it is 9ct, 14ct, 18ct, 19.2ct, 22ct or 24ct. The piece should also be examined for hallmarks. If there is significant wear to the gold, the value will be lower — and if the piece is only gold-plated, it is unlikely to be worth selling at all.

The factors that influence the valuation of a second-hand gold piece are:

• Purity (carat): determines the percentage of pure gold in the alloy;
• Total weight: the heavier the piece, the greater the value;
• Condition: wear, scratches or dents can affect the valuation;
• Type of piece: chains and bracelets tend to command higher values than individual earrings or broken pieces;
• Daily spot price: fluctuates in line with the international market.

Gold Sovereigns (Libras de Ouro) are British coins that have been minted since the early nineteenth century, making them the oldest continuously minted coin in the world. In addition to their intrinsic gold value, many also carry numismatic value — that is, collectible value.

The value of each Sovereign depends on:

• Year of mintage and reign — some reigns are rarer than others;
• Mint of origin — identified by the mint mark;
• Condition — the closer the coin is to mint state (flor de cunho), the higher the value;
• The gold spot price on the day of appraisal.

Sovereigns featuring the Royal Coat of Arms on the reverse are generally more valuable than those depicting Saint George, particularly in commemorative editions.

The condition of the coin is of great importance. If the effigy or the relief details are damaged — even slightly — the coin may lose part of its value. However, a Sovereign will never be worth less than its weight in gold.

The best place to sell gold is always one that inspires confidence and guarantees transparency. Loja do Ouro is a company licensed by the Portuguese National Mint and Official Hallmarking Authority (INCM) and strictly adheres to all legal standards governing the appraisal and purchase of precious metals.

At our network of stores:

• Appraisal is free of charge and carried out by certified appraisers;
• Purchase prices are updated daily in line with the international spot price;
• Payment is immediate, by bank transfer, cheque or cash (up to the legal limit).

We buy and sell gold with integrity, transparency and security — guaranteeing the best market price and a personalised service.

Yes. Gold is widely regarded as one of the safest investments in the world. Unlike fiat currencies or equities, gold retains its value over time and provides protection against inflation and economic downturns.

Key advantages:

• Store of value: gold never completely loses its purchasing power.
• Liquidity: it can be readily sold anywhere in the world.
• Appreciation: during periods of economic instability, gold tends to increase in value.
• Diversification: it is an excellent way to balance an investment portfolio.

For this reason, it is common for investors to hold a portion of their wealth in physical gold — bars, coins or high-fineness jewellery.

Gold is resistant to oxidation and does not rust or tarnish in water. However, frequent contact with chemical products, chlorine, perfume and cosmetics should be avoided. These agents can:

• Diminish the lustre of the alloy;
• Damage the rhodium plating on white gold pieces;
• Weaken solder joints or stone settings.

Recommendation: remove your jewellery before showering, entering a swimming pool or going into the sea — not only to preserve the longevity and original brilliance of your pieces, but also to avoid losing them in the water.

Pure gold does not oxidise, but the metals that make up the alloy — such as copper or silver — can react with chlorine, perspiration, creams or cosmetics, altering the surface tone of the piece. This is a natural process and is fully reversible.

To restore the lustre:

• Wash with warm water and mild soap;
• Use a soft-bristled brush;
• Dry with a soft cloth.

At Loja do Ouro, we offer professional cleaning, polishing and restoration services for jewellery pieces.

Please note: This service is not available in-store and is carried out at our head office. Simply visit any of our stores to receive a quote and arrange for your piece to be sent in for repair.

Learn how to care for your gold jewellery simply and safely:

1. Home cleaning
Mix a few drops of mild liquid detergent in warm water. Leave your jewellery to soak for 15 minutes, then gently scrub with a soft toothbrush. Rinse in clean water and dry with a soft cotton cloth.

2. Pieces with gemstones
Avoid submerging — clean with a damp cloth instead, so as not to damage the adhesive or the setting.

3. Avoid harsh products
Do not use toothpaste, bleach or chemical products — these can scratch the surface and affect the lustre.

For a deeper clean or professional maintenance, bring your pieces to Loja do Ouro, where we can repolish, tighten prongs and restore the original brilliance of your jewellery.

Notes:

• "Mild liquid detergent" — detergente líquido suave rendered precisely; standard English jewellery care terminology.
• "Gemstones" — pedras preciosas rendered as "gemstones" — the correct umbrella term in English for precious and semi-precious stones set in jewellery.
• "Adhesive or the setting" — cola ou o engaste; "adhesive" covers glued stones while "setting" covers prong or bezel-set stones — both are relevant and the distinction is worth preserving.
• "Tighten prongs" — consistent with earlier translations; the correct English goldsmithing term for securing the metal claws that hold stones in place.
• "Bleach" — lixívia is the Portuguese word for household bleach; rendered directly as it is the most commonly understood term in English.