HISTORY AND FOLKLORE

 

             HISTORY AND FOLKLORE

THERE ARE NUMEROUS myths and legends associated with gems. Some tell of cursed stones; others of stones with special powers of: healing, or that protect or give good luck to the wearer. Some of the largest known diamonds have legends associated with them that have been told and re-told over centuries, and many now lost are surrounded by tales of intrigue and murder. Some mines are thought to be cursed - probably a rumour spread by the mine-owners to keep unwanted prospectors away. In Burma, for instance, where all gemstones belonged to the monarch, the belief that anyone who took a stone from a mine would be cursed may have been deliberately cultivated to curb losses of a valuable national asset.

                                     

crystal gazing

Since Greek and Roman times, balls of polished rock crystal have been used to see into the future. The difficulty of finding a flawless piece large enough to be polished adds to the mystique. The mystic gazes at the ball, lets the eyes go out of focus, and then interprets the misty.

 DEATH MASK This Aztec funeral mask adorned with turquoise may have speeded entry to the next world.

 PERUVIAN GOD

 

 This 12th-century ceremonial knife from Peru is made from gold adorned with turquoise. The handle has been formed into the image of a divinity.

THUMB GUARD 

This 17th-century ring. mounted with rubies and emeralds, was protect archers' thumbs when releasing arrows.

BIRTHSTONES 

 Certain gems have traditionally been associated with different months of the year, and are thought lucky or important for people born under their "influence". This probably stems from the ancient belief that gems came from the heavens. Many eultures associate gems with the signs of the zodiac, and others with the months of the year, but the selection varies from country to country, perhaps influenced by availability of gems, local traditions, or fashions. The custom of wearing birthstone jewellery started in 18th-century Poland, and has since spread throughout the world. The most popular selection today is shown right.

CRYSTAL HEALING

 a very long history, as the rituals of medicine men in ancient tribes attest. Crystal healers today believe that each gem has the power to influence the health and well-being of a specific part of the body. The light| reflected off stones placed on vital nerve points is thought to be absorbed by the body, supplying it with healing energy.

ROCK CRYSTAL

 Prized for their beauty and clarity, rock crystals are often chosen for use in crystal healing. 

 

CRYSTAL PENDANT

 Gems worn close to the skin are believed to heal or protect.

GEMS THROUGH THE AGES

GEMS THROUGH THE AGES

PEOPLE EVERYWHERE, throughout history, have followed a natural instinct to collect things of beauty and value, and have used whatever gems they found locally - from shells to sapphires to adorn themselves. Today, the whole range of the world's gems is available to those who can afford them There are more gem-producing areas than ever before, new stones are on the market, and jewellery designs continue to evolve. But the inherent attraction of gems their beauty, durability, and rarity - remains the same.


First Uses

Gem materials were probably first used as much for their durability as their beauty. But beauty was not ignored, even then. For example, the Stone Age obsidian axe below has been wrought to be attractive as well as practical, and ancient civilizations did fashion gems purely for adornment. Although most were primitive in design, some were highly intricate, with painted surfaces. Down the ages, gems have also been offered as prestigious gifts, and their portability and intrinsic value gave them a natural use as currency.

EARLY COLLECTORS 

The earliest collectors found gems with no more equipment than a stick or shovel, a basket, and a sharp eye. Similar Stone Age tools found in the Mogok area of Burma show that rubies have been mined there for thousands of years - and the same methods of panning the stream with wicker baskets are used today. Evidence of more organized early mining - for example, abandoned mines and waste dumps is found in the Urals of Russia, on the shores of the Mediterranean, in Cornwall, England, and in many other places worldwide.

ANCIENT JEWELLERY 

Very little jewellery made before the 18th century services. The best examples are probably those of Ancient Egypt, much of it gold set with gems such as turquoise, lapis lazuli, and carnelian. It shows the great skill of the Egyptian goldsmiths: the gold refined, annealed, and soldered; the probably using silica sand, a technique also known to the Ancient Chinese. The Romans fashioned - went on to develop the polished stone rather than the setting. The art of the goldsmith and lapidary survived in the Dark Ages, though in medieval times gothic style was functional - mainly buckles, clasps, and rings.

UP TO THE PRESENT With the discovery of the Americas in the 15th century, European trade in gemstones expanded, and 16th- ahd 17th-century jewellers could use gems from all over the world. With the rise of an affluent merchant class, jewellery became more widely owned, · and diamonds first became fashionable. In the 20th century, an increase in demand for affordable gems, and the scarcity of the most valuable, will doubtless continue the trend to use more varied gem species in jewellery.

GEM-ENCRUSTED MODERN BROOCH 

Jewellery has passed through many styles, from baroque in the 16th century and floral themes in the 17 th, to art deco and beyond in the 20th.

POLISHING CARVING AND ENGRAVING

PRECIOUS METALS AND GEMS usually I massive, microcrystalline stones and organics-can be worked by polishing, carving, or engraving. Polishing is the oldest form of fashioning. Carving produces three-dimensional objects by cutting them from a larger mass of material. Engraved images are made by scratching out lines or holes, or by cutting away to leave a raised image. Carving and engraving require tools harder than the material being worked.




Polishing

The shine given to the surface of a stone - either by rubbing it with grit or powder, or against another stone - is its polish. Dark- colored gemstones and those that are translucent or opaque, for instance opal and turquoise, are often polished rather than faceted, as are organic gems. They may be polished as beads or as flat pieces to be used in inlay work, or cut en cabochon with a smooth, rounded surface and usually a highly polished domed top and flat base.

Carving

Carving usually refers to the cutting of decorative objects from a larger mass. Stones as hard as 7 on the Mohs' scale were carved in Ancient Egypt, Babylonia, and China. Impure corundum (emery) was used for carving and engraving in India; nowadays a hand-held chisel or turning machine is used. Popular stones for carving include serpentine, Blue John, malachite, azurite, rhodonite, and rhodochrosite

 CHINESE CARVING Carving of gemstones in China dates back to the Neolithic period. The most prized material was imported nephrite jade, and decoratice objects like this model pagoda are still made.

Engraving

 Engraving usually refers to the decoration of the surface of a gemstone by the excavation (scratching out) of lines, holes, or trenches with a sharp instrument, known as a graver or turin. Of all engraved objects, cameos and intaglios are perhaps the most popular. A cameo is a design (often a human profile) in flat relief, around which the background has been cut away. In an intaglio it is the subject, not the background, that is cut away, creating a negative image that may be used as a seal in clay or wax. Intaglios were particuiarly popular with the Ancient Greeks and Romans, and are still prized by collectors.

GOLD ENGRAVING

The surface of gold and other precious metals used in jewellery may be decorated with intricate patterns, using a hand-held chisel called a graver. Engraved gemstones gained prominence in Europe in the Renaissance period. During the Elizabethan period in Britain cameo portraits were often given as gifts, particulariy among the nobility. All through the ages, layered stones have been used for cameos or intaglios, with onyx and sardonyx particulariy popular. Other gems suitable for engraving include rock crystal, amethyst, citrine, beryl, peridot, garnet, lapis lazuli, and hematite, as well as organic materials such as ivory and jet.

MODERN DESIGNS 

This citrine prism, with its clean, architectural lines and exquisite engraving, demonstrates the flair and craftmanship of modern designers. Its maker, Bernd Munsteiner, uses conventional cuts to create classic modern jewels akin to pieces of sculpture. Bernd Munsteiner is one of many artists working in Idar-Oberstein in Germany. Together with Hong Kong, Idar- Oberstein is considered to be one of the most important centres for gemstones today.

Faceting

                            FACETING


THE MOST USUAL METHOD of fashion- features, taking into account its color, fashioning a gem is to cut the surface into a clarity, and weight. He may, however, number of flat faces, known as facets. This gives the stone its final shape, or "cut". The craftsman, or lapidary, who cuts the stone aims to show its best have to compromise to retain weight and therefore value. The blue diagrams on the opposite page show the most popular cuts.


How A STONE IS FACETED

 There are several stages in the cutting of a gemstone, each of which may be carried out by a different expert. In our example, a rough diamond crystal is fashioned into a brilliant- cut. This is the most popular cut for this stone because it maximizes the gem's naturally strong light dispersion. How- ever, because each stone is a different shape, or has imperfections within it, or because retaining the weight is of paramount importance, the cut in its ideal form (the "make") may not be possible. Nevertheless, the essential aim is to make the diamond bright and "sparkling", showing flashes of color called fire. To this end, the size, umber, and angles of the facets are mathematically calculated. The rough crystal is swan or cleaved to obtain a basic workable piece, then turned on a lathe against another diamond to give it a round shape. The facets are then cut and polished in stages, and the stone is given a final polish before mounting.

BRILLIANT-CUTS 

The brilliant-cut is the most popular for diamonds, and for many other stones, particularly colorless ones. It ensures that maxi- mum light is reflected out through the front, giving brightness and fire. Variations in the outline give the oval, the pear- shaped pendeloque, and the boat-shaped marquise or navette.

STEP-CUTS 

The step-cut (or trap-cut) shows colored stones to advantage, having a rectangular or square table facet and girdle, with parallel rectangular facets. The corners of fragile gems may be removed, making octagonal stones - as, for example, in most emeralds.

MIXED-CUTS

 Mixed-cut stones are usually rounded in outline, with the crowns (above the girdle) cut as brilliants, and the pavilions (below the girdle) step-cut. Sapphires, rubies, and most transparent colored stones are cut in this style.

FANCY-CUTS 

These have several possible outlines, such as triangular, kite- shaped, lozenge- shaped, pentagonal, or hexagonal. The cut may be used for rare gems, or to make the most of a flawed or irregularly shaped gem.

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NATURAL INCLUSIONS

                                    NATURAL INCLUSIONS


INCLUSIONS are internal features of gems. They may be solids, liquids, or gases that the crystal enclosed as it grew, or cleavages, cracks, and fractures that filled (or partly filled) after the host material finished growing. Although usually regarded as flaws, inclusions today are often seen as adding interest to a stone. They can also be invaluable in identifying a gem, because some are peculiar to a particular species, while others occur only in a particular locality.


MICROSCOPE

FORMATION OF INCLUSION

Solid inclusions have usually formed before the host stone - the crystals of the host have grown around them and enclosed them. They may be distinct crystals or amorphous masses. Solids and liquid inclusions formed at the same time as the host are aligned to its atomic structure. For instance, the stars in star rubies and sapphires are caused by needle-like crystals of rutile, which formed parallel to the crystal faces at the same time as the host corundum crystals. Cavities filled or fractures healed after the formation of the host give inclusions that resemble feathers, insect wings, or fingerprints.



DIAMOND WITH GARNET

Solid inclusions may be the same gem type as the host,or different like the garnet in the diamond.

PERIDOT "WATER LILY"

 Inclusions that look like water lily leaves are a typical feature of peridot from Arizona, USA. They consist of a central chromite crystal surrounded by liquid droplets.




MOONSTONE "CENTIPEDES" 

These insect-like inclusions  are a common feature of moonstone. In fact they are parallel cracks caused by strain.



RUTILE NEEDLES 

This carved rock crystal perfume bottle contains inclusions of needle-like rutile crystals. Tourmaline and gold are also found in rock crystal.




INSECT IN AMBER

 Insects are sometimes found trapped in amber, caught by the sticky resin as it was exuded. Insects have been added to some imitation amber to create a natural effect..





ALMANDINE GARNET 

Magnified 45 times, the grey patch on the left is a rounded apatite inclusion. The bright interference colours to the right are due to a zircon crystal.





EMERALD (LEFT) 

Rectangular cavities with tails  are some- times found in natural Indian emeralds.

Optical Properties

OPTICAL PROPERTIES

COLOR IS THE MOST OBVIOUS visual feature of a gem, but in fact it is just the optical properties of each gem one of many optical properties, all of which are dependent upon light. The individual crystalline structure of a gemstone  interacts with light in a unique way, and determines species. Effects produced by light passing through a gem are described here; those produced by the reflection of light. 

What makes color?

 The color of a gem depends largely on the way it absorbs light. White light is made up of the colors of the rainbow (spectral colors), and when it strikes a gem some spectral colors are "preferentially absorb- ed". Those that are not absorbed, pass through or are reflected back, giving the gem its color. Each gem in fact has a unique color "fingerprint" (known as its absorption spectrum), but this is only visible when viewed with a spectroscope . To the naked eye, many gems look the same color.

ALLOCHROMATIC GEMS

 Allochromatic ("other-colored") gems are colored by trace elements or other impurities that are not an essential part of their chemical composition. Corundum, for example, is colorless when pure, but impurities in it (usually a metal oxide) create the red stones we know as rubies, blue, green, and yellow sapphires, and orange-pink padparadscha. Allochromatic gems are often susceptible to color enhancement or change. 

DIOCHROMATIC GEMS

 The color of idiochromatic ("self- colored") gems comes from elements that are an essential part of their chemical composition. Thus idiochromatic gems generally have only one color, or show only a narrow range of colors. Peridot, for example, is always green, because the color is derived from one of its essential constituents, iron.

PARTI COLOURED GEMS

 A crystal that consists of different-colored parts is called parti-colored. It may be made up of two colors (bicoloured), three (tricoloured), or more. The color may be distributed unevenly within the crystal, or in zones associated with growth. The many different varieties of tourmaline probably show the best examples of parti-coloring, exhibiting as many as 15 different colors or shades within a single crystal.

PLEOCHROIC GEMS

 Gems that appear one color from one direction, but exhibit one or more other shades or colors when viewed from different directions, are known as pleochroic. Amor- phous or cubic stones show one color only; tetragonal, hexagonal, or trigonal stones show two colors (dichroic); orthorhombic, mono- clinic, or triclinic stones may show three colors (trichroic).

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CRYSTAL SHAPES

CRYSTAL SHAPES

MOST MINERAL GEMSTONES are crystalline, with their atoms arranged in regular and symmetrical patterns, like a lattice; a few are amorphous, with no or only a weak crystal structure. Crystalline minerals may consist of a single crystal, or of many in a group. Polycrystalline minerals are made up of many, usually small, crystals; in cryptocrystalline minerals the crystals are too small to see without the aid of a microscope. Crystalline minerals are made up of a number of flat surfaces called faces; the orientation of these faces defines the overall shape, which is known as the "habit". Some minerals have a single, characteristic habit, such as pyramidal or prismatic; others may have several. A lump of crystalline mineral without a definite habit is called massive. Amorphous gem- stones, like obsidian and tektites, have an irregular shape. Examples of common habits are shown right.

              

CRYSTAL SYSTEMS

Crystals are classified into seven different systems, according to the "minimum symmetry" of their faces. This depends on a crystal's "axes of symmetry"- imaginary lines (shown in black in the artworks on this page) around which a crystal may rotate and still show identical aspects. The number of times the same aspect may be seen - in one 360-degree rotation around an axis - defines that axis as two-fold, three-fold, etc., up to six.