This Gemstones & Collectibles Blow will be dedicated to all aspects of high value gemstones, art, antiques, coins and gold pocket watches. It will also include stories and insights about the gem miners in Colombia, Brazil, Thailand and Zambia.
If a rare piece of art is found in a garage sale this will be written about! A rare coin cache find in a field in the United Kingdom will be news too. The sunken shipwrecks with emeralds, coins and art will be researched. As will the largest gems ever found and dealers in the industry will be news too.
- 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.
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.).
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 .
- How to choose the perfect diamond
Diamond is a natural mineral, the hardest on Earth. The four most well-known quality criteria for assessing a diamond are popularly called “4C”, in English for Carat (Weight), Color (Color), Clarity (Purity) and Cut (Size or Cut).
Diamonds are present in the most important moments of our lives. Each diamond is a world and unique because of its characteristics and precisely because of the interesting combination between its four variables approved by the main diamond certification body IGA (American Gemological Institute), it is internationally accepted to certify the code and value of the four variables.
The cut or size is what allows the light to reflect and refract optimally, making the diamond a light box. These are the main sizes. If you see the round is called bright because it is the one with more facets getting a higher brightness. We consider a very good quality carving when it is proportional to the brilliant ideal. Good when it goes away more than 5%. Average when the deviation is 10% and deficient when it is asymmetric.
Clarity with it measures the purity of the stone. How many and where are the stains and impurities, both inside and on the surface. They are the fingerprints that nature leaves in the diamond and help the experts to distinguish them from the synthetic ones and imitations with the magnifying glass of 10 times that the expert has. Today there are treaties, within the small quilatajes, where the impurities have been bombarded to lower their cost.
The color. The spectrum and diamond color ranges from yellow-brown to colorless, the scarcest and also the most valuable. Some have an exceptional color like green, red, blue, pink … they are fancy diamonds and more expensive than whites. The color of the diamond is graduated on a scale that starts at the letter D and goes down the more color the stone has.
The weight. It is expressed in carats, (0.20 gr) as curiosity coincides just with the weight of the seeds of the carob tree and each carat is divided into 100 points, so a diamond 25 points describes one of 0.25 carats. Know that carats do not determine the value being a feature more influenced by the four variables.
Currently we could talk about a fifth feature that prints “Character” to the diamond that can give life or turn off. They are the right proportions in the size and polish of the facets.
- 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.