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Diamond ruby, sapphire emerald and beryl family gem gold emerald spinel tourmaline

Garnet olivine topaz crystal zircon feldspar group gem

Emerald nephrite opal turquoise serpentine jade dushan jade seasonal jade carbonate jade

Malachite lapis lazuli magnesite (golden powder jade) plum blossom jade chrysanthemum stone bloodstone Qingshan stone Shoushan stone

Pearl amber coral ivory

tower of ivory

As an ornament, ivory has a long history. Due to the long-term extensive use, it has promoted the development of elephant capture industry and made elephants on the verge of extinction. In order to protect this rare animal and maintain the earth's ecosystem, many countries now ban ivory trade.

Ivory refers to two long and curved teeth of an elephant, not all the teeth of an elephant.

Ivory includes African ivory and Asian ivory.

African ivory is generally long, its dentin is relatively hard and milky white, and the best quality is mainly from Tanzania and Cameroon. Asian ivory is generally short, white but easy to turn yellow, of which Sri Lanka is the best.

First, the basic characteristics of ivory

The chemical composition of ivory is hydroxyapatite and organic matter. The ratio of the two is roughly 65:35.

Ivory is generally curved and angular, and almost half of it is hollow. The cross section of ivory is mostly round and nearly round, and its diameter varies with varieties, growing periods and parts. The cross-sectional diameter of the same ivory gradually increases from the cusp to the root.

The cross-section of ivory has a characteristic "Retzius" texture, that is, a diamond pattern formed by the intersection of two sets of interlaced texture lines at an angle greater than 1 15 degrees or less than 65 degrees.

In addition, the cross section of ivory has a layered structure with clear boundaries, which is generally divided into four layers from outside to inside:

Layer I is a dense or concentric layer.

The second layer is a thick "Retzius" line layer, with a large included angle of grain lines, which can reach about 124 degrees, and a wide spacing of grain lines, which is about1-2.5 mm. ..

The third layer is a thin "Retzius" line layer, and the included angle of the lines is smaller than that of the second layer, with an average of about 120 degrees, and the spacing between the lines is very narrow, about 0.1-0.5 mm. ..

Ⅳ layer is dense or hollow.

There are almost parallel small lines on the longitudinal section of ivory.

When ivory is fresh, its color is white, milky white, porcelain white and light rose white, and prehistoric ivory is often blue.

Ivory has a beautiful and soft oily luster, mostly slightly transparent to translucent. The refractive index is 1.54, the hardness is only about 2.5, the specific gravity is usually 1.85, and the fracture surface is cracked and serrated. White-blue to blue-purple fluorescence from weak to strong under long and short wavelength ultraviolet light.

Ivory has excellent toughness.

2. Optimum treatment of ivory

1. bleaching treatment:

It is to soak the ivory that turns yellow or has a yellow tone for a long time in an oxidizing solution such as hydrogen peroxide to remove the yellow, so as to achieve the purpose of improving the grade and value of ivory. Bleaching is a necessary optimization treatment for most ivory.

2. Dyeing treatment:

Dyeing is to soak the ivory with unsatisfactory color in various dyes to get the desired color.

Three. Identification of common imitations

1. Bone products:

Dense bone products are similar to ivory in appearance, refractive index and specific gravity, but their structures are different. Animal bones have hollow tubular structures, and the cross sections of these tubules are circular or oval, and the longitudinal sections are linear. These structures are more obvious when dirt seeps into the hollow pipe.

2. Dumping palm fruit:

Growing in South America and Africa, the skin is brown and the hard shell inside is egg-sized, white or protein-colored. Its hardness, refractive index and fluorescence characteristics are similar to ivory, but its cross section is honeycomb, its longitudinal section is parallel and thick, and there are cell structures in the lines. The proportion of nuts is about 1.4, which is lower than that of ivory.

Soaked in sulfuric acid, ivory will not fade, while nuts are rosy and easy to dye. Nuts have better toughness than ivory, and can be cut with a blade, which is easy to process.

3. Plastic:

Celluloid is the most common and effective ivory imitation material. In order to imitate the stripes on the longitudinal section of ivory, plastic is pressed into thin slices, but this stripe is much more regular than ivory, and it can not produce "Retzius" pattern.

Four. Quality evaluation of ivory

Ivory with rare color or pure white, translucent, dense and tough texture, fine lines and high quality is the best product, while ivory with yellow color, small block and loose structure has low value and even lost jewelry value.

Generally speaking, ivory produced in Africa is fine in texture and fine in section. In Asia, the texture is loose and soft, and the color tends to turn yellow.

Among the evaluation factors of ivory, carving technology is very important. China ivory carving has a long history and unique traditional style, and its carving technology is famous at home and abroad.

Verb (abbreviation of verb) the origin of ivory

Ivory is mainly produced in Africa, such as Tanzania, Senegal, Ethiopia and Gabon. The quality of ivory produced near Pangari in Tanzania is the best, followed by Thailand, Myanmar, Sri Lanka and India in Asia.

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