Gemstones (Semi Precious Stones)

Since the beginning of human civilization, man has used precious stones and gems in multifold ways: as ornament, as sacred elements in religious rituals, as divining tools, in astrology, healing and more.
Stories and legends were written about the beauty and magic of the stones. Kings set them in their crowns, warriors and seamen held them as talismans, religious people used them in their symbols, and doctors and sorceress used them in their practices.
Today we encounter many different beliefs regarding the power of precious stones.
Some are believed to have the power to strengthen and amplify the positive qualities of man, while others are thought to prevent disasters and protect man from disease and negative influences. Some gems are thought to fortify and balance the "Chakras" - the energy centers of our bodies, while others are thought to create a protective shield around the human aura or energy field.
In any event, it is difficult to remain unmoved by the beauty and power of these gemstones. The variety of shapes and spectrum of colors represent the magnificence of creation in nature.

Components:

Gemstones can be divided to two main groups:
1. Organic – stones originating from flora and fauna (e.g. pearl and coral from fauna ; amber and jet from flora)
2. Inorganic – stones originating from minerals found in rocks deep in the earth. The minerals transform under heat and pressure which exists deep in the earths crust and crystallize into unique formations of stones as they come out and cool on the surface of earth. The combination of minerals, the depth inside earth and duration of crystallization, determine the shape and color of the stone.
The structure of inorganic stones is divided to two kinds:
A. Crystal - a substance with regular arrangements of atoms which has some external unified shape (geometrical symmetry) regardless of its source.
B.  Amorphous - substance whose internal composition does not have a specific form. The structure and shape of an amorphous stone is largely a result of the space and conditions where it was formed.

Shape and color:

Gemstones are found in nature in a large variety of sizes, shapes and colors. At the stage of "process and polish", the shape and final design of the stone is determined.
In some stones we can see inclusions - fragments or bubbles that were locked inside in one stage or other during crystallization or cracks that were formed during extreme changes of pressure or temperature.

The origin of colors in stones is caused by two factors:
1.  The color of the stone is determined by its dominant mineral component. For example, in Turquoise, the blue, green color comes from the copper found in the stone, while the Garnet's red color comes from iron. 
2.  Stones which crystallize with no dominant color but are penetrated during formation, for example, in the corundum family of stones, the penetration of a very small quantity of the earths crust will determine the red color of the Ruby and penetration of iron or titanium will give the (Sapphire) its blue color.

In some stones we can see special effects of light and color, which act as important factors in determining the value of the stone. Following are several examples:
Play of colors - On the surface of stone we see flashes of light in a blaze of colors created due to the special structure of the stone. In Opal for example, crystallized silica presents as minute spherical particles arranged in such a way that spectral colors are produced by diffraction.
Cat's eye effect - Very narrow parallel hollow tubes cause a chatoyant effect – a line of light crosses the stone and moves when moving the stone.
The star effect - Flashes of light reflected in the stone as a shape of star due to dichroism (the property of presenting different colors in two different directions).
Milky light, whitish or blue opalescence produced by the crystals from within the stone that filter the light reflected in it. This effect can be seen in Moonstone.
Aventurescence - A ray of light reflected from translucent stone created by inclusions glittering in the light. This effect is typical to Sun Stone.

Characteristics and Criteria

There are three criteria which characterize and determine the value of gemstones:
1. Beauty - The beauty may lie in color, clarity and opalescence of the stone. "Professional agreement" exists regarding the ideal color for each stone. The colors in some stones have special names like the most wanted shade of color in Ruby is called "Pigeon's Blood Ruby" and a rare color of the Emerald is called "Grass Green".
In others the response of the stone to light is what makes it beautiful.
2. Rarity
3. Durability - Criterion is divided to following categories:
A. Hardness - The level of durability of a stone in withstanding wear and tear. It is possible to estimate hardness in terms of resistance to external stresses like scratching. The hardness is expressed in terms of an empirical scale consisting of ten sample minerals of increasing hardness, each of which is capable of scratching the preceding mineral and being scratched by the subsequent one. Known as "Mohs' scale".
B. Toughness - The resistance of the stone to cracks and blows.
(Hard stone not necessarily tough one, Diamond for example is the hardest stone on earth but may crack easily. On the other hand Amber has relatively low hardness but its toughness level is high and it can last longer.
C. Chemical and Heat Resistance - Durability of color and structure of stone after exposure to sunlight, heat, moisture and contact with chemicals and acids.

Organic gemstones are characterized by low rank of hardness and high sensitivity to environmental conditions. Pearl for example may change its color and even peel due to storage in unsuitable conditions.
In order to preserve their beauty, it is important to keep gemstones in places which are well-ventilated and with sufficient light (though not in the sun). This is especially important for organic stones.

It is recommended to wear gemstones set in jewelry which enables the natural moisture of the body to feed the stone and so help maintain its luster.
(On the other hand, direct contact of gemstones with perfume, cream, oils and cosmetics can be damaging, so it is recommended to wear your jewelry only after creams etc have been completely absorbed by the skin.)

In the following list some of the stones set in Li-Art jewelry, are presented with a description of qualities and virtues related to each stone.

It is recommended however, that when choosing a piece of jewelry or precious stone, to pay attention to ones personal feeling of attraction, rather than choosing according to the stated characteristics or zodiac sign attributed to a particular gemstone.