Sapphire

Sapphire is classified as a precious or fundamental gem along with ruby, emerald and diamond.

It can be of different colors such as orange, green, or yellow but the most valuable are those of intense blue or gentian blue. Some cabochon-cut sapphires have the optical effect of a star inside.

Physical properties:

  • Hardness: 9 on the Mohs scale
  • Specific gravity: 3.9 – 4.1
  • Conchoid fracture

Optical properties:

  • Color: Blue, Orange, Green, etc.
  • Vitreous shine, and can occasionally appear silky
  • Variable transparency, and possible presence of inclusions that give a milky appearance.

 

Sapphire producing countries.

First of all, a clarification, since you have to differentiate between origin and provenance.

Origin means the country where the mine is located and origin is where it is marketed and handled. For example, we can have a sapphire whose origin is a mine in Sri Lanka and its origin is Thailand because it is here where it has been carved and commercialized.

Thailand is the main sapphire carving and trading country in the world, yet it barely has a few small mines.

The main deposits in the world are in Madagascar where sapphires of exceptional quality have been found. Sri Lanka, too, remains one of the main producers, its quality having been considered the highest for many years. So when we talk about a Ceylon sapphire (ancient name for Sri Lanka), we are talking about sapphires with magnificent color. Finally we find deposits in Thailand, Australia, Cambodia, China and Vietnam.

 

Value a sapphire

Sapphires are valued based on their color, purity, size, and size.

  • Colour: Unlike diamond, there is no color scale so there is great subjectivity in this regard. In principle, sapphires with an intense blue color but with life and transparency would be the most valuable color. A gray or green veil mixed with blue would decrease its value, and when blue is mixed with violet it increases it (Ceylon color). As the degree of color intensifies, the stone loses transparency, so there is to find an intermediate between intense color and transparency. The light must pass sufficiently but at the same time allow an intense color. Very dark (Australian) blues have a lower value.

    To value a sapphire, it is important to know if the color is natural or heat-treated, and to what extent. Today most of the sapphires are treated in origin.

  • Purity: Regarding purity, we will say that the fewer inclusions (impurities) there are and the purer the sapphire, it will also be more valuable.
  • Size: Sapphires generally come in oval or emerald cut. The cabochon cut (rounded) is the least valuable, since the sapphire is not of sufficient quality to give it facets.
  • Weight: Sapphire is a relatively abundant stone, so its price will be lower than that of rubies or emeralds. Sapphires larger than one carat increase significantly in price.

 

Famous sapphires

Star of India:

The Star of India is the largest star sapphire in the world weighing 563.35 carats. Discovered in Sri Lanka some 300 years ago, it is now in the American Museum of Natural History in New York. Grayish-blue in color, with a slightly milky quality caused by the presence of rutile. However, rutile is also responsible for the effect of the star, an effect known as asterism. Aside from its staggering size, the Star of India is also unusual in that it has stars on both sides of the stone.

Stuart Sapphire:

It is one of the oldest known sapphires, dating back to 1214 at 104 carats. It has a beautiful blue color, and the gem has passed through the hands of several kings and cardinals before being mounted on the crown of Queen Victoria. Eventually, it was replaced by the Star of Africa, so that the Stuart sapphire now rests on the rear of the British imperial state crown.