| Ruby | |
|---|---|
 A ruby crystal from Dodoma Region, Tanzania | |
| General | |
| Category | Oxide mineral variety |
| Formula (repeating unit) | aluminium oxide with chromium, Al2O3:Cr |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (3 2/m) |
| Space group | R3c[1] |
| Identification | |
| Colour | Orangy red through strongly purplish red. |
| Crystal habit | Terminated tabular hexagonal prisms |
| Cleavage | No true cleavage |
| Fracture | Conchoidal, splintery |
| Tenacity | Brittle |
| Mohs scale hardness | 9.0 |
| Luster | Subadamantine, vitreous, pearly (on partings) |
| Streak | White |
| Diaphaneity | Transparent, translucent |
| Specific gravity | 3.97–4.05 |
| Optical properties | Uniaxial/− |
| Refractive index | nω=1.768–1.772 nε=1.760–1.763 |
| Birefringence | 0.008 to 0.010 |
| Pleochroism | Strong: purplish-red – orangy-red |
| Dispersion | 0.018 |
| Ultraviolet fluorescence | Red under longwave |
| Common impurities | Cr. (sometimes :Ti, Fe) |
| References | [2] |
https://en.wikipedia.org/wiki/Ruby
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 parts of the Crown Jewels of the United Kingdom, with a history dating back to the middle of the 14th century. It has been in the possession of England's rulers since it was given in 1367 to its namesake, Edward of Woodstock (the "Black Prince").[2] The stone is believed to have originated from the Badakhshan mines in present day Afghanistan[3] and Tajikistan,[4] the principal source of large spinel gems in the Middle Ages.
Spinel
All red gemstones used to be referred to as rubies or "balas rubies". It was not until 1783 that spinels were chemically differentiated from rubies.[5] They both have aluminium, oxygen, and a little chromium, but spinels also have magnesium, which rubies lack.
https://en.wikipedia.org/wiki/Black_Prince%27s_Ruby
May is the fifth month of the year in the Julian and Gregorian calendars and is the third of seven months to have a length of 31 days.
May is a month of spring in the Northern Hemisphere, and autumn in the Southern Hemisphere. Therefore, May in the Southern Hemisphere is the seasonal equivalent of November in the Northern Hemisphere and vice versa. Late May typically marks the start of the summer vacation season in the United States (Memorial Day) and Canada (Victoria Day) that ends on Labor Day, the first Monday of September.
May (in Latin, Maius) was named for the Greek goddess Maia, who was identified with the Roman era goddess of fertility, Bona Dea, whose festival was held in May. Conversely, the Roman poet Ovid provides a second etymology, in which he says that the month of May is named for the maiores, Latin for "elders," and that the following month (June) is named for the iuniores, or "young people" (Fasti VI.88).
Eta Aquariids meteor shower appears in May. It is visible from about April 21 to about May 20 each year with peak activity on or around May 6. The Arietids shower from May 22 – July 2, and peaks on June 7. The Virginids also shower at various dates in May.
https://en.wikipedia.org/wiki/May
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