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Blue John (also known as Derbyshire Spar) is a semi-precious mineral, a rare form of fluorite with bands of a purple-blue or yellowish colour. In the United Kingdom it is found only at Blue John Cavern and Treak Cliff Cavern at Castleton in Derbyshire. During the 19th century, it was mined for its ornamental value, and mining continues on a ...
Lapis lazuli (UK: / ˌ l æ p ɪ s ˈ l æ z (j) ʊ l i, ˈ l æ ʒ ʊ-,-ˌ l i /; US: / ˈ l æ z (j) ə l i, ˈ l æ ʒ ə-,-ˌ l i /), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color.
Many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. [12] For example, diamonds, which have a cubic crystal system, are often found as octahedrons. [13] Gemstones are classified into different groups, species, and varieties.
The Black Prince's Ruby is a large, irregular cabochon red spinel weighing 170 carats (34 g) set in the cross pattée above the Cullinan II diamond at the front of the Imperial State Crown of the United Kingdom. [1] The spinel is one of the oldest gems in the Crown Jewels of the United Kingdom, with a
The regalia contain around 23,578 gemstones, among them Cullinan I (530 carats (106 g)), the largest clear cut diamond in the world, set in the Sovereign's Sceptre with Cross. It was cut from the largest gem-quality rough diamond ever found, the eponymous Cullinan, discovered in South Africa in 1905 and presented to Edward VII.
Even the captain was unaware that his "precious" cargo was a decoy. [19] On 10 February 1908, the rough stone was split in half by Joseph Asscher at his diamond-cutting factory in Amsterdam. [20] At the time, technology had not yet evolved to guarantee the quality of modern standards, and cutting the diamond was difficult and risky.
This is a list of gemstones, organized by species and types. Minerals. There are over 300 types of minerals that have been used as gemstones. Such as: A–B
After color follows clarity: similarly to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated. Ruby is the traditional birthstone for July and is usually pinker than garnet , although some rhodolite garnets have a similar pinkish hue to most rubies.