In Sanskrit, Blue Sapphire is called as nelashma, neelratna,shaniratna, Indraneel etc. In Persian it is called as Yakoot or kabood.
Blue Sapphire is basically Corundum and comes in many other colors as well. But traditionally sapphire is associated with blue color only. The chemical composition is Aluminium Oxide.
Good quality Blue sapphire is found in Burma, Shri Lanka and India. The best Indian Sapphire is cornflower blue is found in Jammu and kashmir, Montana in USA also produces blue sapphire. Cambodia, Brazil, Kenya, Malawi and Colombia also produce this sapphire. The sapphire has hardness of 9, specific gravity 4.00, refractive index 1.76-1.77 with a Trigonal crystal structure.

Real blue sapphire shines by its own rays and does not borrow light. IT is very smooth and the color has special effect as if emerging out of its core. If placed in a transparent milk pot on a full moon light, It will give the bluish color to the person holding the pot also. An unreal stone would give a depressed blue color.
Blue sapphire is the precious stone for Saturn. The consecration of Blue sapphire should be done on any Pushya constellation day. Otherwise, It can be worn there is amritsiddhi yoga time or the day governed by Shani-Pushya. It is advisable to wear it in an alloy called Triloha, But sometimes it is prescribed in "Gold" as well.

Medical Effect:

The stone is said to be increasing eyesight,longevity and blood flow to organs. It helps decrease rheumatism, sciatica, neurology, epilepsy, hysteria, tumor, reduces fat, arthritis, nerve pains, mental illness, petrochemical and radiation miasma, excessive bleeding, emotional pain and trauma, hemorrhage. It provides balance to intestinal tract, pancreas, lower spinal column, heart, blood, and adrenals.

Astrological Effects:

The blue sapphire adds wealth, widens the sphere of one's influence on the other people particularly if one is dealing with the masses. There is also an increase in social status and prosperity. Saturn controls most diseases in the body; by wearing a blue sapphire, one is assured of a long and healthy life.

Wearing Blue Sapphire ( Ascendant wise analysis)

• Aries:

For Aries ascendant, Saturn becomes the lord of the 10th and 11th house. Both are good houses but ownership of 11th house has not been considered good for these natives. Even then Saturn in 2nd,4th,5th,9th,10th,11th houses or lagna will give beneficial results during dasa of saturn.
Blue Sapphire in such cases can be worn only during Saturn Dasa.

• Taurus:

For Taurus native saturn is lord of 9th and 10 th house. here it becomes yagakarka. If these natives wear blue sapphire, then they will always be prosperous, acquire status, material benefits and prosperity. It can be worn with Diamond by such persons to derive even better results.

• Gemini:

For Gemini native,Saturn is lord of 8th and 9th house. It is considered beneficial as it owns 9th house here. B lue Sapphire can be worn by these native along with Emerald for benefits. Saturn Dasa is the best time to wear Blue Sapphire.

• Cancer:

For cancer natives, Saturn owns 7th house and 8th house. 7th house is marak house and 8 th house is of death. Saturn is not considered a good planet for these natives. They should never wear Blue Sapphire.

•  Leo:

Here Saturn owns 6th house and 7 th house. Both are not good places. These natives should never wear blue Sapphire.

• Virgo:

Saturn here owns 5th house and 6 th house Since it owns 5th house, it is not bad for such natives.But these persons should wear blue sapphire only during the dasa of Saturn.

• Libra:

Saturn owns for such natives both 4th and 5th houses. Here it is yagakaraka planet. It is extremely beneficial. These natives should wear Blue Sapphire for material benefits,fixed assets and gains from then.Saturn is friend of Venus, The lagna lord, as well. Here it will give very good beneficial to the native if Diamond is also worn along with Blue Sapphire.

• Scorpio:

For these native, Saturn owns 3rd and 4th house. It is not considered a good planet for these persons. They should avoid wearing Blue Sapphire. If Saturn is placed in 5th, 9th, 10th,11th house, only then it can be worn during Saturn dasa. 

• Sagittarius:

Here saturn owns a marak house 2nd and 3rd house which is Dusthana. Saturn is malefic for these natives. Saturn is not friendly with lagna lord jupiter as well. These natives should not wear Blue Sapphire.

• Capricon:

Here Saturn is the owner of Lagna and 2nd house. These natives should wear Blue Sapphire always for properity and material benefits.

• Aquarius:

Here also Saturn is the owner of lagna 12th house. For these natives, it gives good results. The people should wear Blue Sapphire for life to get protection from ill health and for general prosperity.

• Pisces:

For these natives, Saturn is the lord of 11th and 12th houses. It is considered malefic planet for these natives. Saturn is enemy of lagna lord Jupiter. Even then for material gains. these natives can wear blue sapphire during Saturn dasa but it is advisable for these natives to avoid wearing blue sapphire as it does more harm than good.