Gemstones

Agate

Agate got its name from the Greek philosopher and naturalist Theophrastus of Eresos because it was found in large quantities in a river called Achates (now Dirillo) in Sicily. In mineralogical terms, the stone, which is very varied in colour, belongs to the quartz family and is particularly valued as a gemstone due to its colourful and striped veining. There are also single-coloured varieties and artificially coloured stones. Agate appears in a transparent to translucent form. It looks particularly harmonious in a cabochon cut. Its Mohs hardness is between 6.5 and 7.  

Amazonite

Amazonite is a light to dark green or turquoise-coloured stone. It is found in Brazil, among other places, but not in the Amazon, as its name mistakenly suggests. It belongs to the mineral class of silicates. The opaque stone is mainly offered as a table or cabochon cut jewellery stone. It is usually made into ball chains, earrings or even pendants and rings. Its Mohs hardness is between 6 and 6.5 and it is sensitive to acids and alkalis.

Amethyst

The origin of its Greek name "amethystos" - which means "counteracting intoxication" - expresses the belief that the wearer of an amethyst is immune to the intoxicating effects of wine. The gemstone, which is particularly popular as a precious stone, belongs to the quartz mineral group and occurs in all shades of the colour violet. The dark violet-coloured stones are particularly valuable. Amethyst is a transparent to translucent stone and can be cut in various faceted shapes or as a cabochon. To prevent fading, the amethyst should be protected from strong, direct sunlight. Amethyst has a Mohs hardness of 7.

Aquamarine

Aquamarine - which means "water of the sea" - is a fascinating gemstone with a particularly broad spectrum of blue tones. It contains all shades from sky blue to azure blue. The most intense shades of blue are among the most valuable. The gemstone, which belongs to the beryl family (ancient Greek "beryllos" for blue-green stone), is characterised by great transparency and is available in many different cuts. Its hardness (indicated on the Mohs scale from 7.5 to 8) makes it largely insensitive to scratches. The stone enchants with its extremely beautiful lustre.

Aventurine

Aventurine, whose name is derived from the Italian "a ventura" and means "by chance", belongs to the quartz family of rocks. Small mineral inclusions in aventurine appear as light-coloured reflections and give the greenish stone a playful sparkling effect, which is known as aventurisation. A cabochon cut particularly emphasises this light reflection. Aventurine is one of the most popular jewellery stones. It is usually used to make bead necklaces, bracelets, earrings and pendants. Its Mohs hardness is between 6 and 6.5.

Rock Crystal

The ancient Greeks thought it was a kind of frozen water and therefore called it "krystallos" = ice. It was not until the 18th century that the word "mountain" was added, indicating where it was found. In fact, it can be found almost everywhere in the world. Its crystal-clear appearance, which can always have small inclusions of gases and liquids, is reminiscent of the appearance of ice cubes. Its price depends on its purity, so crystal-clear stones are always more expensive than stones with inclusions. As a jewellery stone, we often find it in ball chains and bracelets. Rock crystal is a variety of the mineral quartz and has a hardness of 6.5 to 7 on the Mohs scale.

Amber

Amber (succunite) is a clear to opaque stone made from fossilised resin. With a Mohs hardness of 2 to 2.5, it is a soft material. It fascinates with its different colours, high light refraction and golden-yellow lustre. Its rich colour palette ranges from yellow to orange and brown. When polished, amber shimmers in a honey colour. It can also be ivory-coloured due to mineral inclusions. The name of amber is derived from the Low German word "börnen", which means "to burn". Amber feels sensual and warm and is surprisingly light. The largest and best-known place where amber is found is in the former East Prussia, in the "Samland" region around Königsberg. The magnificent and legendary Amber Room, which was last exhibited in Königsberg Castle, has been missing since the end of the Second World War.

Carnelian

Carnelian ("corneolus" = Latin word for cherry) is an opaque to slightly translucent gemstone that belongs to the quartz family as a variety of chalcedony. It gets its orange-red to brown-red colour from its iron content. The higher the proportion of iron oxide in carnelian, the redder it is. If the proportion of iron hydroxide is higher, the carnelian has a browner colour. However, carnelians can also be changed in colour by heat. It is mainly found in Brazil, India and Uruguay. Carnelian is used exclusively for the production of gemstones. Its degree of hardness on the Mohs scale is 6.5 to 7.

Citrine

The bright lemon yellow colour gave this stone from the quartz family its name. It is derived from the Latin "citrus" for lemon. However, natural citrines are quite rare and could not meet the high demand for this stone. Artificial citrine is therefore often found on the market. These are orange-yellow, burnt amethysts. Although the stone can be described as insensitive to scratches with a score of 7 on the Mohs scale, it is relatively sensitive to acids. The transparent stone is usually cut faceted and then set in gold or silver.

Diamond

Nothing seems more valuable than a diamond. It is undisputedly the most coveted, the most radiant and also the stone with the most followers worldwide. The diamond is quite simply the king of gemstones. But what is so special about this stone, which is the only gemstone traded on the stock market? After all, the diamond consists of nothing but carbon. Its name, derived from "adamas" - the unconquerable - stands for its hardness. It was only from the 13th century onwards that people succeeded in working the hardest of all stones. The technique known today as the brilliant cut was not developed until around 1910. It is also the cut that gives the diamond its incomparable fire and makes it literally shine from within. As a piece of jewellery, we find it in every conceivable variation. However, the classic engagement ring is usually a white diamond solitaire. The price of a diamond is defined by the 4Cs: clarity, cut, colour and carat, and there are various international designations for the declaration of diamonds.

The following tables provide an overview of the different designations for the colour grading and clarity of a diamond.

Colour Scale

Purity Scale

Note: For any product made from rough diamonds mined since 1 January 2003, we guarantee that the diamonds come from legitimate sources and have been procured in accordance with United Nations resolutions. We guarantee that, to our knowledge and/or written guarantees from the supplier, the diamonds are not associated with conflict. For any product made from rough diamonds mined before 1 January 2003, we warrant that to the best of our knowledge and belief, conflict diamonds are not knowingly sold and that we will take reasonable measures to prevent the sale of conflict diamonds. The diamonds for sale at Rhomberg are, to the best of our knowledge and/or written guarantees of the supplier, exclusively of natural origin and untreated.

Garnet

The red varieties of garnet are the best known. These red stones used to be popularly known as "carbuncle stones". Although there are certainly 16 different types within the garnet group in a wide colour spectrum, the pyrope, almadine and spessartine, which all have a red colour, are best suited for jewellery. In general, a garnet is transparent to translucent in colour. The stone is popular for its lively sparkle, which it owes to its high light refraction. With a hardness of 6.5 to 7.5, it is also one of the least sensitive gemstones. Most garnets today come from South Africa, India and Sri Lanka.

Haematite

Haematite is a highly ferruginous, opaque mineral. Even in ancient times, the stone was coveted as a jewellery due to its extremely shiny surface. When the black-grey haematite is polished, the grinding dust colours the cooling water red, which is why the stone got its name haematite from the Greek word haima, which means "blood". Its hardness is between 5.5 and 6.5 on the Mohs scale. The stone can react sensitively to acids. Haematite is usually offered in cabochon or facet cut. The largest deposits are found in Brazil, China, England, India, New Zealand, the Czech Republic and the USA.

Coral

Even in ancient times, people were fascinated by the bright red colour of coral. There are thousands of different types of coral, but only the hard precious coral is suitable for jewellery making. Its colour varies from light orange to dark red. As corals are naturally matt, they are usually polished for jewellery, giving them a beautiful shine. They are mainly used to make bead necklaces or cabochon-cut creations. Precious coral is found off the coasts of Corsica, Sardinia and Tunisia, among other places. Its Mohs hardness is 3 to 4 and as it is an organic gemstone, it should not come into contact with acids or be exposed to excessive heat.

Artificial pears

Artificial pearls or imitation pearls are produced with the aim of imitating natural pearls. Artificial pearls should not be confused with cultured pearls. There are many different ways of producing imitation pearls. One of the best known is the Mallorcan pearl, which is produced using a relatively complex process. Nevertheless, in contrast to real pearls, imitation pearls are usually much cheaper and, depending on the manufacturing process, even less sensitive. Imitation pearls are also often dyed to produce pieces of jewellery in trendy colours. herzustellen.

Labradorite

Labradorite is a relatively common mineral mixture from the feldspar group. Its iridescent play of colours with a metallic sheen, known as "labradorescence", is striking. These light effects are also what fascinate the observer about it. Important sites are Québec and the Labrador Peninsula in Canada, which gave the stone its name. It is also found in the Ukraine, Finland, Norway and Madagascar. Its Mohs hardness is between 6 and 6.5 and the stone reacts sensitively to acids and alkalis. To avoid dulling the surface, it should not be cleaned in an ultrasonic bath.

Lapis lazuli

Its name is made up of the words "lapis" (stone) and "lazulum" (blue). It is a naturally occurring deep blue rock that is made up of different minerals in varying proportions. Small golden pyrite flecks are often found in the stone, giving it a pretty sparkle. Thanks to its ultramarine blue colour, opaque lapis lazuli is a highly sought-after gemstone. Lapis lazuli is usually offered as a bead necklace or in a cabochon cut. Its Mohs hardness is 5 to 6 and it is mainly mined in Russia, Chile and Afghanistan.

Malachite

Malachite takes its name from the Greek malaché "mallow", a flowering plant with dark green leaves. The opaque stone has an intense green colour and only occurs in this form. Malachite is a common mineral that has been found in over 8800 locations worldwide. A special feature of malachite is its beautiful banding, similar to wood grain, in different shades of green. It is mainly used as a gemstone, but must be handled with care as it only has a Mohs hardness of 3.5 to 4 and a low density.

Moissanite

Moissanite - named after its discoverer, the French Nobel Prize winner in chemistry, Dr Henri Moissan - is a stone that exceeds all expectations of a gemstone in terms of luminosity, hardness and durability. This is probably also the reason why the mineral sample from a meteorite that fell in Colorado (USA) was initially mistaken for a diamond.  In 1904, Moissan was then able to examine a larger quantity of the meteorite and recognised from the typical hexagonal crystals that the meteorite contained silicon carbide. Silicon carbide is formed at the high temperatures that occur when meteorites hit the earth. Due to its rarity, naturally occurring moissanite is not used commercially. However, the first artificial production of silicon carbide was achieved in 1891. It was not possible to produce moissanite in gemstone quality until 1997. Since then, the stone, which has a slightly lower Mohs hardness (9.25) than a diamond (10), has often been used as a diamond substitute. Moissanite gets its striking brilliance from the double refraction of light in the stone. It sparkles in all the colours of the rainbow. In sunlight, it sparkles almost hypnotisingly.

Moonstone

Moonstone belongs to the group of feldspars. It is milky white, grey, brown, orange or rarely black. If you move it, a soft bluish-white shimmer glides over its surface, reminiscent of moonlight. The slightly translucent stone has an enchanting lustre that is best shown to advantage in a cabochon cut. It is used exclusively as a jewellery stone and is mainly found in Sri Lanka and India. Its Mohs hardness is 6.5 to 7.

Morganite

Morganite, named after the well-known New York private banker and collector J.P. Morgan, belongs to the beryl mineral group. Due to its colour, which ranges from pale pink to salmon to violet, the stone is also known as pink beryl. The stone has become particularly popular in recent years due to the trend towards pastel colours. It can be transparent or translucent, whereby transparent stones are often faceted and translucent stones are usually offered in cabochon cuts. It is found in Afghanistan, Brazil, China, Madagascar, Mozambique, Namibia, Zimbabwe and the USA. Its Mohs hardness is given as between 7 and 8.

Onyx

Onyx is an opaque black variety of chalcedony and mineralogically belongs to the quartz family. This extremely popular gemstone has a beautiful effect in both cabochon and faceted cuts. Its use as a gemstone is extremely diverse. It is found in Brazil, the USA, Mexico, India and Madagascar. On the Mohs scale, it lies between 6.5 and 7.

Opal

Opal was already one of the most sought-after stones in ancient times. Its name is derived from the Latin "opalus", which means "precious stone". Opals are formed by siliceous fluid accumulations in different rocks. There are numerous varieties, which in turn have their own names depending on their colour and appearance. Opals sparkle most beautifully when cut into cabochons, allowing the full colour spectrum of the rainbow to unfold. This unique play of colours is also known as "opalescence". One exception is the fire opal, which is mostly found in Mexico, is almost transparent and is usually offered in a facet cut. Opals are exclusively processed into gemstones. Australia is the world's most important supplier of opals. The Mohs hardness of opal is between 5.5 and 6.5.

Peridot

Peridot, formerly also known as chrysolite, is a particularly pure variety of the mineral olivine. While olivine is a widespread mineral, peridot is rather rare in gemstone quality. It occurs exclusively in green. Its colour spectrum ranges from a fresh light green to a lush dark green to olive green tones. It is mainly mined in Brazil, Australia, the USA, China, Pakistan, Myanmar, Kenya and Norway. The translucent stone is usually cut faceted. Its Mohs hardness is 6.5 to 7.

Pearls

Pearls are considered a true jewellery classic. They are naturally beautiful. Unlike gemstones, they do not have to be polished to reveal their splendor. With the discovery that pearls can be cultivated and no longer have to be retrieved from the depths of the sea at the risk of one's life, they have become affordable for many people since the beginning of the 20th century. They are cultivated in China, Australia and the South Seas. The price increases with perfection: the rounder and smoother a pearl is, the more expensive it is. Then its shimmer, the so-called lustre, comes into its own. Pearls come in various natural shades such as white, pink, gray and gold.

Nacre

The term "mother of pearl" refers to the shell from which the pearl comes. However, mother-of-pearl also known as nacre can also be obtained from numerous other molluscs (gyro snails, red-mouthed snails, etc.), which form a flat shell. The basic colour of mother-of-pearl ranges from white to pink to light grey. Depending on the angle from which it is viewed, it reveals a rainbow-colorued iridescence, known as "iridescence", which has fascinated people with this natural material for thousands of years. In jewellery processing, the art consists of sawing pieces of mother-of-pearl to an exact fit and working them into the intended pieces of jewellery in a mosaic-like manner. All pieces of jewellery created in this way are unique.

Prasiolite

Prasiolite, also known as green quartz, is a leek-green (Greek "prason" = leek, "lithos" = stone) transparent variety of quartz. This coveted gemstone is rarely found in nature. It is found in India, Russia and Zimbabwe. It is mainly produced by firing amethyst or yellow quartz. Stones produced in this way should not be exposed to direct sunlight as they could fade. The stone is usually offered in a facet cut. It is 7 on the Mohs hardness scale.

Quartz

With a Mohs hardness of 7, quartz is a hard mineral and is often used as a gemstone due to its beautiful appearance and good processing properties. It occurs in a wide variety of colours and its crystal surfaces have a glassy sheen. From clear, colourless rock crystal to black onyx, there are numerous quartz crystals in a wide variety of forms. The most important locations are in Brazil, India, Madagascar and the USA. In Europe, the Alps and the Urals are among the main places where quartz is found.

Smoky quartz

Strictly speaking, smoky quartz is a rock crystal that is given a darker or lighter smoky brown colour by natural radiation, depending on where the stone is found. The stronger the radiation, the darker the colour of the stone. It is mostly transparent to translucent and is only used to make gemstones. The stone is usually offered faceted and cut. Its Mohs hardness is 7.

Rose quartz

Rose quartz is a variety of the mineral quartz in delicate pink shades. The opaque to translucent stones are offered in cabochon or facet cut. They are used to make necklaces, pendants, rings and earrings. Rose quartz has a Mohs hardness of 7 and is mainly found in Brazil, India, Madagascar, Mozambique, Namibia, Sri Lanka and the USA.

Ruby

Genuine rubies are the most valuable of all coloured gemstones. They are a variety of corundum, the second hardest mineral after diamond, and have a Mohs hardness of 9. Their colour can vary between a pale and a dark red. The name ruby is derived from the Latin "rubinus" = red. The most important ruby deposits are located in Myanmar, Thailand and Sri Lanka. Since the end of the 19th century, it has been possible to produce usable rubies artificially from corundum, making ruby an affordable gemstone. It is possible to intensify the colour by firing. When cut, clear stones are usually given a facet cut, while stones with optical effects are given a cabochon cut.

Sapphire

Sapphire belongs to the corundum mineral group. It includes all colourless and coloured varieties of corundum except ruby. However, people usually think of blue stones when they talk about sapphire. Hence its name from the Greek "sappheros" = blue stone. It has a hardness grade of 9 and is therefore almost as hard as a diamond. The sapphire looks most beautiful in a facet cut. It is often combined with diamonds, which gives it a royal touch. Significant sapphire deposits are found in Australia, Myanmar, India, Cambodia, Kashmir, Madagascar, Sri Lanka, Tanzania and the USA. Since 1910, sapphires of perfect quality can also be produced synthetically, making the stone affordable.

Emerald

As the most precious stone in the beryl group, emerald is one of the "big four" gemstones alongside diamond, ruby and sapphire. Its name is derived from the Greek "smaragdos", meaning green stone. It is also the colour by which the value of an emerald is judged. The stronger the colour, the more expensive the emerald. The transparent stone can also have inclusions, but this is not at all undesirable; it is then referred to as a "jardin", a garden enclosed in the stone. Emeralds are generally available in all cuts, but the clear emerald is at its most beautiful in the "emerald cut" specially developed for it. Thanks to its Mohs hardness of between 7.5 and 8, the emerald is largely insensitive to scratches. Important deposits are in Colombia, Brazil and the Urals.

Sodalite

Sodalite is a less common, mostly opaque mineral from the feldspar group. Its name is made up of the Greek "sodium" for sodium and "lithos" for stone and refers to its high sodium content. The colour of sodalite is a dark, warm blue, often interspersed with light (almost white) or dark (almost black), irregular lines or spot-like areas. Due to this spotted coloration, sodalite is usually offered in cabochon cuts or made into bead chains. It is mainly mined in Brazil, Namibia and Canada. Its Mohs hardness is between 5 and 6. Care should be taken with boiling water, as it can extract sodium and chlorine from the sodalite.

Spinel

Spinel is a relatively rare mineral from the oxide class. Particularly beautifully formed crystals are used as gemstones. Due to a possible natural admixture of metal ions such as iron, chromium, zinc, cobalt or manganese, the otherwise colourless spinel appears in an astonishing spectrum of colours. The red spinel (ruby spinel) looks confusingly similar to ruby. Spinels can also be produced synthetically. Remarkably, their chemical properties hardly differ from those of natural stones. Impurities that occur in natural stones can be completely avoided in the laboratory. Spinel has a Mohs hardness of 8 and is therefore insensitive to scratches. The most important spinel deposits are in the USA, Myanmar, Sri Lanka, Tanzania and Afghanistan.

Tanzanite

Tanzanite is a blue variety of the gray to greenish mineral zoisite. Its rarity makes it an extremely exclusive gemstone. The country of origin, Tanzania, provides information about its name. However, a large proportion of the tanzanites on the market today are produced from gray-brown to yellow-brown zoisite by firing at around 400 to 500 C. What is particularly fascinating about it is its multi-colored appearance, which can be blue, violet or even bronze depending on the viewing angle. This multi-colored appearance is called "pleochroism". The larger the stone, the more intense its colour appears. With a Mohs hardness of 6.5 to 7, the stone must be treated with care to avoid scratches. We do not recommend cleaning in an ultrasonic bath. The stone is also sensitive to acids.

Tiger's eye

The tiger's eye got its name because the golden-brown variety of quartz resembles a tiger's eye when cut. This so-called "cat's eye effect" is particularly beautiful in the cabochon cut. The stone, which is used exclusively for jewellery production, has a clearly visible fibrous structure and a silk-like sheen. Tiger's eyes are mainly found in South Africa and Western Australia. Its hardness is 6.5 to 7 on the Mohs scale.

Topaz

Topaz is a common mineral with the peculiarity of forming huge crystals, which is why even larger stones are not overly expensive in the jewellery trade. It is mainly found in Brazil, but also in Myanmar, Nigeria, Pakistan, Russia, Sri Lanka and Tanzania. In nature, topaz occurs in many different colours. Among the coloured specimens, the natural blue topaz is rather rare and therefore expensive. To enhance its delicate blue, it is usually given a subsequent colour treatment, resulting in stones in intense shades of blue ("Sky Blue Topaz", "Swiss Blue Topaz", "London Blue Topaz"). Topazes of other colours can be dyed blue through subsequent refinement such as heating and ionization. With a Mohs hardness of 8 and its glass-like shine, topaz has become an extremely sought-after gemstone, which is usually offered in a facet cut.

Turquoise

Turquoise is one of the oldest gemstones in human history and was used long before the stone came to Europe by ancient American cultures (Mayas, Aztecs), the ancient Egyptians, the Persians and many Native American tribes. Even today, turquoise is mainly used in traditional Native American style jewellery. Turquoise is a secondary mineral that is formed by weathering and oxidation of existing minerals or rocks near the surface. It is found in Iran, Afghanistan, the USA, Mexico, Brazil, Argentina, Australia, China and Tanzania. Pure turquoise reaches a maximum Mohs hardness of 6 (equivalent to window glass). Depending on the formation conditions, the stone can also be more porous, in which case it is improved by oiling and waxing before cutting. The cabochon cut is the main feature of turquoise.

Zirconia

Zirconia is the most brilliant imitation of diamond jewellery. It looks confusingly similar to a diamond and is also extremely popular in the jewellery industry due to its hardness on the Mohs scale of between 8 and 8.5. It can be cut just like a diamond, for example in a brilliant cut. But cubic zirconia also cuts a fine figure in a cabochon cut. Another plus is that cubic zirconia can be produced in any colour, making trendy and elegant creations possible at affordable prices.