Sapphire

According to Rebbenu Bachya, the word "Sapir" in the verse Exodus 28:20 means "Sapphire" and was the stone on the Ephod representing the tribe of Issachar. Sign can denote any of the following:. The major deposits are: Sri Lanka, Thailand, Burma, Cambodia, Nigeria, Madagascar and Australia. To write one's signature on a document, thus showing authorship and will. It refers to a "blue gem," either the sapphire proper or possibly lapis lazuli. Commercial signage, including flashing signs, such as on a retail store, factory, or theatre. The word sapphire is probably Phoenician in origin, coming to English from the Ancient Greek word σάπφειρος, through the Latin sapphirus. Similar terms which are more specific are character, letter or grapheme.

Wafers of single crystal sapphire are also used in the semiconductor industry as a substrate for the growth of gallium nitride based blue and green light emitting diodes. Within a writing system, a sign is a basic unit. Such slices are used as watch faces in high quality watches, as the material's exceptional hardness makes the face almost impossible to scratch. In most parts of the world these include stop signs, speed limit signs, cross walk signs, and others. Pure sapphire ingots can be sliced into wafers and polished to form transparent crystal slices. On (the side of or above) roads there are traffic signs to instruct drivers. In these lasers, a synthetically produced sapphire crystal with chromium or titanium impurities is irradiated with intense light from a special lamp, or another laser, to create stimulated emission. Information signs are notices that instruct, advise, inform or warn people.

It can also be easily modelocked. In semiotics, sign (semiotics) are the basic units of meaning. While this laser has few commercial applications, the Ti-sapphire laser is popular due to the relatively rare ability to tune the laser wavelength in the red-to-near infrared region of the electromagnetic spectrum. In medicine, a medical sign is objective evidence of the presence of a disease or disorder, as opposed to a symptom, which is subjective. The first ever laser produced was based on the ruby chromium impurity in sapphire. In biology a sign is an indication of some living thing's presence. As well as gemstone applications there are many other uses:. In mathematics, the sign of a number refers to whether it is negative or positive.

Synthetic sapphire crystals can be grown in cylindrical crystal ingots of large size, up to many inches in diameter. In linguistics, Ferdinand de Saussure described a Sign (linguistics) as a combination of a concept and a sound-image. Sapphire is also the birthstone associated with September. In divination a sign is an omen, an event or occurrence believed to fortell the future. Cornflower blue is one of the most popular colors for sapphires (the other choice color a deep royal blue), though there is little objective consensus about which shade of blue is the most cornflower or the most desirable. See signedness and signed number representation. Lady Diana Spencer's engagement ring from Charles, Prince of Wales was a sapphire ring. In computing, the digits where one bit among them tells the number is either negative or non-negative are called signed, otherwise unsigned.

It weighs 423 carats (84.6 g). In communication sign or signing refers to communicating via hand gestures, such as sign language. The Logan sapphire is one of the largest blue sapphire gems known. In astrology sign is often used to mean the Sun sign. A manufactured star sapphire called the Linde Star shows a very regularly-shaped and distinct asterism because the formation process is more tightly controlled than it is in nature. Although natural sapphires can show an asterism, the shape of the star is usually somewhat irregular and sometimes indistinct.

A version which shows an asterism is called a Star sapphire (see picture above). The tell-tale sign of synthetic sapphires is the crystalline growth lines which are usually curved due to the pulling during the accelerated crystal growth process. The chemical compositions and physical properties are identical to the natural sapphires. Gem quality sapphires and rubies occur naturally and can be easily and cheaply produced in the laboratory.

They have a hardness of 9 on the Mohs hardness scale (Diamond is 10). The crystals are exceptionally hard, with only diamond being harder among natural gems. Traces of iron and titanium give sapphires a blue color. Pure sapphire is transparent.

It is the impurities in the aluminium oxide crystal that give the color variations, with different impurity chemical elements giving the different colors that can be found. They were found in many countries especially in Asia such as India, Sri Lanka, Thailand, Myanmar, and Cambodia. However a pink-orange sapphire, called a padparadsha, is highly prized. Pink, yellow, green, white, and parti-color (multi-colored) sapphires are often valued less than the blue variety of the same quality and size.

When color is not specified, sapphire refers to the blue variety. (The red variety of corundum is also known as ruby.). Sapphire is any gemstone-quality corundum that is not red. .

It can be found naturally as gemstones or manufactured in large crystal boules for a variety of applications. Sapphire is the single-crystal form of aluminium oxide (Al₂O₃), a mineral known as corundum.