The name spinel may have been derived from the Greek word spitha, meaning “spark”, or perhaps spinthir, meaning “scintillate”. Spinel is a mineral and gemstone that has been prized for centuries for its brilliance, durability and range of colours. It occurs in several hues, including red, pink, orange, blue, violet, green and black. Historically, red spinels were frequently mistaken for rubies because of their similar appearance and because the two gemstones were often found in the same deposits. It was only in the 18th century that spinel was recognised as a distinct mineral. Spinel is composed of magnesium aluminium oxide, while ruby is the red variety of corundum and consists of aluminium oxide coloured primarily by chromium. Red spinel ranges from orangish-red to purplish-red, while ruby is generally associated with vivid red hues, including the highly prized pigeon’s-blood red.

History of Spinels
Some of the finest historic spinels came from Badakhshan, in the Pamir mountain region between present-day Afghanistan and Tajikistan. The Kuh-i-Lal mines, overlooking the Panj River, are among the oldest known sources of spinel. The mines are mentioned in early historical and mineralogical accounts, including writings attributed to the Persian scholar Al-Biruni in the late tenth or early eleventh century. From the medieval period onwards, Badakhshan spinels travelled along the Silk Road and entered royal and imperial treasuries across Asia and Europe. The mines remained an important source of fine spinels for centuries, producing the celebrated red and pink stones historically known as balas rubies. Spinels also held an important place in the Mughal treasury. The Mughal emperors accumulated large quantities of precious stones as symbols of wealth and sovereignty, and gemstones formed a dedicated part of the imperial treasury. Historic Badakhshan spinels are associated with collections including the Iranian Crown Jewels, the Ottoman collection at the Topkapi Palace Museum and the British Royal Collection.

Famous Spinels
Black Prince’s Ruby
Despite its name, Black Prince's Ruby is a red spinel rather than a ruby. One of the most celebrated stones in the British Crown Jewels, it has a history dating to the 14th century and is set prominently in the Imperial State Crown. It passed through Spanish and English royal collections before becoming part of the Crown Jewels. Its history is traditionally traced to the 14th-century Kingdom of Granada, from where it passed to Pedro of Castile and, in 1367, to Edward of Woodstock, the Black Prince, in return for military assistance. Believed to have originated in Badakhshan, the stone belonged to a class of red spinels historically known as balas rubies. Tradition further associates it with Henry V, who is said to have worn it on his helmet at the Battle of Agincourt in 1415. It later entered the English Crown Jewels and was incorporated into Queen Victoria's Imperial State Crown in 1838. In contemporary times, the Black Prince’s Ruby remains a significant component of the British Crown Jewels. The use of the Imperial State Crown in ceremonial events, such as the State Opening of Parliament, showcases the continuity of British traditions.

The Timur Ruby
The Timur Ruby is another historic gemstone that was long believed to be a ruby but was later identified as a red spinel. The stone bears the engraved names of several Mughal and other rulers. Its history connects it to the Timurid, Mughal, Persian, Afghan, Sikh and British imperial worlds before it entered the British Royal Collection in the 19th century. The stone was traditionally associated with Timur, who was believed to have acquired it following his sack of Delhi in 1398. It subsequently passed through the hands of Timurid and Persian rulers before reaching the Mughal emperor Jahangir, who had his name and that of his father, Akbar, engraved upon it. Shah Jahan later added his name and is associated with placing the stone in the Peacock Throne. After Nadir Shah's invasion of Delhi in 1739, the spinel travelled through Afghanistan and eventually came into the possession of Shah Shuja, who surrendered it to Ranjit Singh in the Punjab. Following the British annexation of Punjab in 1849, it was taken to England with other treasures from the Lahore Treasury and presented to Queen Victoria in 1851.

Characteristics of Spinels
Spinel is generally transparent to opaque and is valued for its brilliance, colour, clarity and durability. Unlike ruby, spinel is singly refractive, meaning that light travels through it without splitting into two rays. Natural spinel commonly occurs as octahedral crystals and has a Mohs hardness of approximately 8, making it suitable for jewellery.

Colours and Varieties of Spinels
Spinel occurs in a wide range of colours and varieties. Red and pink spinel range from orangish-red to vivid red and pale to hot pink. Important sources include Myanmar, Sri Lanka and Vietnam. Cobalt spinel is a rare blue variety coloured by cobalt and is known for its vivid blue colour. Black spinel is an opaque, iron-rich variety valued for its even black colour and high lustre. Thailand and Mexico are notable sources. Gahnospinel is a rare zinc-bearing variety that ranges from violet to dark blue. Sri Lanka is an important source. Gahnite is another zinc-rich variety, ranging from dark green to black. It is mainly valued by mineral collectors for its distinctive crystals.