Precious stones and gemstones are minerals (and, in some cases, organic materials, such as coral) prized for their colour, lustre, transparency and durability, and used in jewellery. In this section, you will find detailed guides on the most sought-after gemstones: their meaning, properties, origin, treatments, care and how to buy them.
In the traditional classification, the four precious stones are the diamond, the ruby, the sapphire and the emerald. The others, such as amethyst, topaz, aquamarine and tourmaline, are known as semi-precious stones, a commercial term that does not reflect the beauty or value of each stone.
To evaluate any gemstone, it is worth knowing its hardness on the Mohs scale (ranging from 10 for diamond to much softer gemstones, such as malachite), as well as its colour, inclusions, cut and any treatments. If you are just starting out, read the guide to identifying a precious stone or gemstone first.
Check the hardness, lustre, inclusions (using a 10x magnifying glass) and density. Home tests are not conclusive, and for high-value items, it is best to request a gemmological report.
Ask for a certificate from a recognised gemmological laboratory (such as GIA or IGI), a receipt and written information regarding any treatments, such as heating, irradiation or impregnation with oil or resin.
Traditionally, precious stones are diamonds, rubies, sapphires and emeralds. The rest are referred to as semi-precious stones, but this is a commercial term, and some gemstones outside this group, such as Paraíba tourmaline, can be very valuable.
Consider colour, clarity, cut, carat weight, origin and treatments; compare them with market prices and check the gemmological report. Each gemstone has its own criteria, and colour tends to be the most important factor for many of them.
Generally speaking, use warm water, mild soap and a soft brush, and store each piece separately to avoid scratching. Avoid chemicals, ultrasound and steam on fragile or treated gemstones, such as emeralds, opals, coral and malachite.
For low-value items, it is not compulsory, but for high-value purchases or for resale, the report is strongly recommended.
Aquamarine is a blue to blue-green gemstone, widely used in jewellery and known as the birthstone for March. In this guide, you’ll learn about the symbolism and meaning of aquamarine, its characteristics (colour, hardness, lustre and treatments), where it comes from and how to look after your jewellery. Aquamarine is […]
Pindobaçu, in the north of Bahia, is known as the emerald capital. The municipality, with a population of around 19,000, lies in the Bahian hinterland and is home to part of the Serra da Carnaíba mountain range, where emerald mining began in the 1960s and which remains the town’s main […]
The ruby is one of the world’s most valuable gemstones. The name comes from the Latin ruber, which means ‘red’. In this guide, you’ll learn about the significance of the ruby, its characteristics (colour, hardness, lustre and treatments), where it comes from and how it is used in jewellery. A […]
The quartz stone is one of the most commonly used gemstones in jewellery and one of the few coloured stones you’ll find in almost every jewellery shop. In this guide, you’ll learn about the meaning of quartz, its properties and characteristics, the different varieties and colours (rock crystal, amethyst, citrine, […]
The emerald is the green variety of beryl and one of the most highly prized gemstones in jewellery. In this guide, you will learn about the significance of the emerald, its characteristics (colour, hardness, lustre, treatments and quality), where it comes from and how it is used in jewellery. The […]
Topaz is a gemstone known for its variety of colours, good hardness and vitreous lustre. In this guide, you will find the properties and characteristics of topaz (composition, hardness, density, refractive index and care), its colours and treatments, the history of the rare imperial topaz from Ouro Preto (MG) and […]
Jade is a gemstone that has been used since prehistoric times and is prized in many cultures. In this guide, you will learn about the meaning of jade, its properties and characteristics (jadeite and nephrite), the different varieties and colours, treatments and the A, B and C classifications, and how […]
The agate has been prized since ancient times and is known for its coloured bands, which form unique patterns in each piece. In this guide, you’ll find out about the meaning of agate, its properties and characteristics, the main varieties, dyeing, its use in jewellery, care instructions and production in […]
The amethyst is the violet or purple variety of quartz and the most striking gemstone in this group. In this guide, you’ll find out about the meaning of amethyst, its properties and characteristics, how it is graded, where it is found, the treatments it undergoes (including heat treatment to produce […]
The tiger’s eye is a variety of quartz ranging in colour from gold to brown, with silky bands of light that appear to move when the stone is turned. In this guide, you’ll learn about the meaning of tiger’s eye, its properties and characteristics, how it is formed, its varieties […]
The sapphire is a blue variety of corundum and one of the most prized coloured gemstones in jewellery. In this guide, you’ll find out about the meaning of the sapphire, its properties and characteristics, its colours, origin, asterism (star sapphire), synthetic varieties, treatments, how it is graded, its use in […]
Jewellery made from different species of coral catches the eye with its colour, which ranges from deep red to pale pink and white. In this guide, you will learn what coral is, its properties and characteristics as a gemstone, the species most commonly used in jewellery (noble coral, bamboo coral, […]
Paraíba tourmaline is a variety of tourmaline that comes in neon blue, blue-green or green, and is one of the rarest and most highly prized gemstones in the world. In this guide, you’ll learn about the history of its discovery in Brazil, its gemmological properties and characteristics, why it has […]
The diamond is the world’s best-known gemstone and the classic symbol of engagement jewellery. In this guide, you’ll learn about the characteristics of diamonds (composition, hardness, brilliance), the significance of the stone, how it features in jewellery, what the 4 Cs are (carat, colour, clarity and cut) and how to […]
The malachite stone is an unmistakable gemstone: its intense green colour, marked by stripes and rings of different shades, is unlike that of any other stone. In this guide, you’ll find out what malachite is, the meaning traditionally attributed to it, its gemmological properties and characteristics, its origin, its use […]
Tourmaline is one of the gemstones most commonly used by jewellery designers, as it comes in almost every colour – and often features more than one colour within a single stone. In this guide, you’ll find out what tourmaline is, its gemmological properties and characteristics, the main varieties (Paraíba, indicolite, […]
Knowing how to identify a precious stone or gemstone is becoming increasingly important, as imitations and lab-grown gemstones are getting better and better. In this guide, you’ll learn the difference between natural, synthetic, artificial and imitation gemstones, discover the main Brazilian gemstones (beryls and tourmalines) and learn how to use […]
The opal is one of the world’s most admired gemstones, and Brazil has its own source of precious opal in Pedro II, in Piauí. In this guide, you’ll find out about the meaning of opal, its properties and characteristics, the different types and colours, the opal from Pedro II (Piauí), […]
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