Emerald
Hardness: 7.5-8 specific gravity: 2.65-2.80
Refractive index: 1.57-1.60 birefringence: 0.006-8
Wear: fragile, avoid hand cream and water vapor
Emerald is the most valuable green gem. It has a kind of "bright green" that other gemstones can't match. Gemologists use emerald green to describe this unique color. Emerald is one of the five precious gemstones.
Emerald belongs to beryl family, and its main component is beryllium aluminosilicate (al2be3 [si6o18]). It is bright green because of containing trace chromium (CR). The content of chromium is also the basis of judging whether a green beryl can be called emerald.
Emerald is the birthstone of May.
The knowledge of emerald
The word "Emerald" comes from the Greek word "smaragdos", which means "green stone". In ancient times, the word may also be used to refer to all green gemstones. Ancient Egyptians mined emeralds in 1500 BC.
In the book of talismans, published in 1914, emerald is described as: "wearing a ring inlaid with emerald strengthens memory and prevents dizziness."
Characteristics of emerald
In addition to its bright colors, emerald is also characterized by abundant inclusions and few large particles with completely pure interior, which is affected by the coloring composition and mineral growth environment. Because of its many contents, gemologists would describe the interior of an emerald as Jardin, which means "garden" in French.
There are many cracks in natural emerald, and it has strong brittleness. In order to improve the purity and reduce the risk of processing, cutting and grinding, the emerald raw stone is often immersed in colorless ceder wood oil once it is mined, until it is cut.
This treatment, known as "immersion", is the only natural optimization accepted and recognized by gemologists.
The formation and origin of emerald
Most of the emerald crystals grow in metamorphic and hydrothermal deposits, the most important producing areas are South America and Africa. Generally speaking, the highest quality emeralds are produced in Colombia, South America. Zambia, Africa, is one of the new emerald producing areas in recent years, and it is common to see pure large grain protoliths.
In addition to Colombia and Zambia, other gem emerald producing areas include Brazil, Zimbabwe, India, Afghanistan, Pakistan, the Russian Ural region, etc.
Factors affecting prices
The influencing factors of emerald price are very complex. In addition to the common weight, color and purity, they are also affected by the origin and optimization treatment. Each factor may produce multiple price differences.
Color: the high-quality emerald produced by Muzo mine, Colombia's most famous mining area, presents a kind of deep brilliant green with a blue tone. Gemologists will also call the emerald reaching this color level "Muzo green". The closer it is to this color, the more expensive it is.
Cleanliness and Optimization: almost all emeralds have been optimized for cleanliness. In the "immersion" treatment, "slight" and "minor" are acceptable treatment grades. It should be noted that "resin filled" emeralds are not recognized as a treatment, and the price is only less than one tenth of "oil soaked" gemstones.
Origin: the price of emerald from Colombia is three times higher than that from Zambia.
Wearing and preservation
Emerald is the most vulnerable of the five precious gemstones. It can only be cleaned with mild soapy water and soft hair brush. It is not allowed to use ultrasonic cleaner.
In daily wear, pay attention to avoid collision, avoid hand cream, water vapor contact with gemstones.
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