Category: Color Precious Gemstones

Types of deposits and geographical distribution of gems


Gems are found in almost all types of rocks, although with different frequency in each other. If taken together, they probably constitute the group of minerals that best represent the variations in pressure and temperature that can give rise to the different types of known deposits in the earth’s crust. They can be formed by primary crystallization from acidic, intermediate, basic and ultrabasic magmas, by recrystallization in metamorphic rocks, by weathering and dragging of pre-existing rocks, by chemical precipitation, by organic action and by the combined action of all the previous processes.

Types of deposits of the main gems.

Excluding diamonds, which alone constitute 90% in value of all marketed gems, and pearls, which today are practically all cultivated, the gems are distributed in the different deposits as follows:

Approximately 25% of all gems have an igneous origin, mainly pegmatitic.

30% can be found in metamorphic nesting rocks, whether they are calcareous or non-calcareous.

Another 30% corresponds to deposits of aqueous origin (hydrothermal, surface circulating water, etc.)

15% to gems of organic origin (amber, coral, ivory, etc.).

Geographical distribution of the main gems.

From a geographical point of view, all continents have important deposits of gemological material:

In Asia there are the most important ruby deposits, especially in Mogok and Hong-Hsu ( Myanmar, former Burma ). In Southeast Asia (Thailand , Myanmar, Indochina and Sri Lanka) are, in turn, the most important deposits of sapphires , spinels and zircons , in Kashmir (India) the best sapphires have appeared, from Afghanistan stand out their exceptional lapis lazuli, large jade deposits are found in Myanmar and China , while historically, diamond and many varieties of quartz have had some of their main deposits in India . In Siberia (Russia) there are important deposits of diamond, chrysoberyl and many other gems.

The most important and varied stones found in South America are found in the Brazilian shield. The State of Minas Geraes is justly famous for its abundance and variety in gems; diamonds, topazes ,emeralds, aquamarines, morganites and other beryls, spinels, garnets, kunzites, tourmalines, quartz of all varieties and practically all pegmatitic gems, as well as many of the metamorphic ones appear.

Spain is a country, as a whole, poor in gems.

  • It lacks diamonds , which have been unsuccessfully investigated in the ultrabasic massifs of Ojén and Carratraca (Málaga) and in the ultrapotassium volcanic rocks of Jumilla (Murcia). Detailed gemological research has been published by various authors (García Guinea, Galan).
  • Beryls are frequent, but not gem quality.
  • Some emeralds , of very little gemological value, have been found in the complex of Lalín (Pontevedra).
  • Also blue-green aquamarines , some large, in Pereña and other towns in Salamanca .
  • There seems to be no corundums or spinels of gem quality.
  • Tourmalines , abundant in the granitic massifs of the Western Peninsula, are always black (chorlo) and therefore have no gemological value.
  • Colorless and blue topazes have been found in the Valle de la Serena (Badajoz), but they are far from the value of the imperial topazes of Brazil.
  • Citrine and smoky quartz of large size and good quality have been found in Villasbuenas ( Salamanca ) and variscita in Palazuelos de las Cuevas (Zamora).
  • Garnets in various locations ( Níjar , Salamanca , La Coruña , etc.).
  • Some agates and chalcedony of a certain beauty and few other things.

In the United States of America there are important deposits of sapphires, garnets, spodumene, tourmaline, turquoise, topaz, red beryl and other gems. In Mexico , fire and noble opals are famous, as well as amethysts from the state of Guerrero. The topazes of San Luis Potosí also stand out, as well as the Nephrites and Obsidians .

Africa is also an extraordinarily rich continent in gems. There are diamonds in great quantity and with gem quality in South Africa , Ghana , Angola , Bostwana , Namibia , Sierra Leone , Democratic Republic of the Congo , Tanzania and other countries of Central and Southern Africa. Chrysoberyl, emerald, garnets, sapphire and ruby, tiger’s eye, tourmaline and zircon in Zimbabwe , South Africa , Kenya and Tanzania . Olivine and turquoise in Egypt . Madagascar is very rich in quartz, feldspar, garnet, scapolite, sphene, spinel, spodumene, beryl and many other gems.

Finally, Oceania is also a very rich continent, although the discoveries are more recent. Australia is one of the world’s leading producers of diamonds (highlighting, among others, the rare and valuable “fantasy” diamonds), and has large deposits of sapphire, opal, spinel and turquoise .

Sapphire Rose, Purple Sapphire

Sapphire presents a very varied palette of colors. There are pink sapphire, purple sapphire, sunset red sapphire, white sapphire, yellow sapphire …

In this article about gems and precious stones I am going to talk about the sapphire Rose and purple Sapphire.

According to the intensity of the color, you can see more details on the same subject.

These gems exist in pastel pink shades as well as darker shades, which are closer to the rubies and carry in their name or description the prefixes of fuse or magenta to name them.

There are some of these varieties of sapphire that are directly ruby. In this debate, even the ICA (International Colored Gemstone Association) has intervened.

The most common form in which these gems are found is the oval size or the shape of the magazine, which is how you can best appreciate its qualities. Although they can also be found in other forms, as with all precious stones.

The most frequent places of origin are Australia, Madagascar, Sri Lanka, Tanzania and Thailand.

As for the variety of purple sapphire, the historical name of this gem is “oriental amethyst”. However, in the difference of the Amethyst. However, you have to compare the stones in beauty. As with the sapphire Rosa, I refer purple, it desists in several shades that are darker or lighter and close to the reddish tones. The value of these stones is based more on the personal taste of each one.

A look at the emerald trade from rough crystals to gemstones and how the offices work in Colombia

An exceptionally large, finest rough emerald crystal from Muzo. This was offered at $45,000 wholesale price in Bogota’ in 2004. It cut two stone (match pair) of squares 7 cts. each.

Viewing an emerald rough with loupe on the famous Catorce or emerald market in Bogota.

Many of the brokers are women. My best stone during that trip, an exceptionally clean Muzo stone, heart shape of 5.65 ct. was purchased from a beautiful, female broker…nothing new about this selling tactic…except that it works well for the seller.

Checking emeralds. To know emeralds quality and price takes a lot, lot of experience. Checking emeralds under special loupe. A careful, close-up examination is very important. There are many synthetics offered to foreign buyers.

A fine parcel of emerald crystals is examined. Technician checking more emeralds at a typical office. A master cutter, initializing the cutting process of an exceptional emerald crystal. This process is thought through very carefully before the cutting begins.

The master cutter’s wheel and examining the emerald crystal and try to decide how to get rid of the included section (whitish portion in the emerald crystal). Probably that occurred when the crystal was broken away from the rock host (matrix).

Here is the final result: Finest color, top clarity and awesome cutting for this finest match pair, 8.5 cttw. from the Muzo crystal seen previously. In Colombia, top emeralds are called “gota de aceite”, that means “oil drop”. Were offered for sale in November 2004 in Bogota for several thousands of USD per carat.

Top Emerald Mining Countries of the World

Emeralds are gemstones from the beryl family. Rough emerald deposits are typically found in metamorphic rocks, and their unique greenish hue attracts people from all walks of life. There was once even an ancient decree passed that only royalty and nobles were allowed to wear such an extravagant jewel.

Fortunately, times have changed. These days, anyone can freely purchase and enjoy quality emeralds from any number of countries.

Rough Emeralds, Then & Now

In ancient days, rough emeralds came from Egypt. Queen Cleopatra, the last Pharaoh of Egypt, was a true devotee of this precious stone. Mines near the Red Sea were even named after the captivating queen, because of her intense love for this rare and beautiful jewel.

During the mid-1600’s, Spain discovered Muzo, the Indian’s secret mine for rough emeralds. The largest mines of rough emeralds were found hidden deep in the Andes mountain ranges.

What are the Top Emerald Mining Countries of the World?

Rough emeralds out in the production of these stones. Here is a look at the top mining countries for rough emeralds:

  1. Colombia. The mountain ranges of the Andes are located in Colombia. There are three major mines in this region: Muzo, Chivor and Coscuez. Two of these mines are leased by the government to private companies.
  2. Brazil. The emerald mines of Brazil are located in the states of Bahia, Minas Gerais and Goias. Some say they are now producing rough emeralds that well rival the ones mined in Colombia.
  3. Zambia. The majority of the gems produced in Zambia are found in the Kamakanga and Kagem mines. Both are found in the northeastern region of the country.
  4. Zimbabwe. This country produces rough emeralds from the Sandawana mine, located in the southwest of the country. Emerald production here is not as high compared to some other countries.
  5. United States. Beaver County, Utah is home of rough emerald production in the US. The mines are located in the eastern slopes of the Wah Wah Mountains.

What are the Distinguishing Characteristics of Emeralds from Different Countries?

Colombian  rough emeralds are highly prized because of their deep green color. Emeralds of dark green are generally much rarer. These emeralds are found only in the deepest part of the Andes ranges.

Brazil produces rare cat’s-eye emeralds and very rare six-spoke star emeralds. No other country has ever produced such a magnificent type of rough emerald.

Zambia is known for mining deep green rough emeralds, similar to those found in Colombian mines. The finest stones they have are clear, grass-green in color but somewhat smaller than the darker ones.

Zimbabwe’s rough emeralds are small in size, but are some of the finest. Their color is bright green, with warm yellowish undertones.

The United States is the only country to produce one of the world rarest gemstones: the Red Emerald. These are only four carats, but more rare and more expensive than diamonds.

If you have the same passion for rough emeralds as Queen Cleopatra, you should take care to purchase stones that are highly graded. When it comes to emeralds, the world is your oyster. So to speak!

Emerald Gems Good for Investment?

Is your birthday in May? If so, lucky you the stunning green emerald is your birthstone! A scarce gem, the emerald is a symbol of beauty, status and power, valued particularly for its rich color.

Many people purchase emerald gems and emerald jewellery simply for their beauty and appeal perhaps as a romantic keepsake or special gift for a loved one without even considering their value as an investment. How many people do you know who buy emeralds for their cash value?

Although emerald gems are not as popular as stock investments, there are savvy jewelers and investors who consider acquiring emerald gems as assets a serious business, and one that rivals the difficulties of many conventional investment vehicles.

There are many things to consider when purchasing an emerald for its investment value. First, let answer one very important question:

Are Emeralds Good for Investments?

The answer is a big YES! Here are some solid reasons why emerald gems could make a great contribution to anyone investment portfolio:

  1. They’re small and easy to store unlike stocks, cash, or real estate and other traditional forms of investment; valuable emerald gems are conveniently small in relation to their cash value. Just imagine: a gem worth $10 million could fit in the palm of your hand! This makes emerald gems the ultimate investment vehicle for non-detectable and easily kept assets. You don’t need a big bank vault or an army of accountants to keep track of them for you!
  2. Private and anonymous investments currently, transactions related to emerald gems and other precious stones do not require reporting to government agencies, as long as you’re a private owner and not an emerald dealer. This means you can invest in emerald gems without having them listed as part of your public records. Private investors can store emerald gems wherever they wish, be it a bank vault or a personal safe. This is ideal for investors who want to keep their assets safe from prying eyes.
  3. Emeralds gems don’t easily fluctuate in value unlike stocks and mutual funds that require regular checking to keep your money afloat and earning, emerald gems command a stable value in the market, and can save you the hassle of constantly checking the stock market and moving your funds from one stock to another.

As we know, today economy is facing high levels of inflation, and this trend is expected to continue. For this reason, investing in emerald gems is a good idea, since their values don’t plummet like stocks and other traditional investments. Even when the price of high quality diamonds fell by 20%, emerald gems held their value some even saw a price increase.

If you want to start buying emerald gems as an investment, be careful about where you get your emeralds. Be diligent in researching information before making a purchase. Check the emerald’s color, clarity, carat and weight. Emerald gems hold their value over time and their price is expected to go up as time goes by. Choose your emeralds carefully who knows how much your wise investment could be worth after a few years!