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2. List of sapphires by size - Wikipedia

   en.wikipedia.org/wiki/List_of_sapphires_by_size

   Sapphires are a precious gemstone, a variety of the mineral corundum, consisting of aluminum oxide (α-Al 2 O 3) with trace amounts of elements such as iron, titanium, chromium, copper, or magnesium. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors.

3. Star of India (gem) - Wikipedia

   en.wikipedia.org/wiki/Star_of_India_(gem)

   The Star of India is a 563.35-carat (112.67 g) star sapphire, one of the largest such gems in the world. [1] [a] It is almost flawless and is unusual in that it has stars on both sides of the stone. The greyish-blue gem was mined in Sri Lanka [3] and is housed in the American Museum of Natural History in New York City.

4. Sapphire - Wikipedia

   en.wikipedia.org/wiki/Sapphire

   Star sapphire 68 carat star sapphire in round mogul cut - men's ring version - 750 yellow gold - Russian goldsmith - handmade around 1990. A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism; red stones are known as "star rubies".

5. List of rubies by size - Wikipedia

   en.wikipedia.org/wiki/List_of_rubies_by_size

   Some gemstones that are popularly or historically called rubies, such as the Black Prince's Ruby in the British Imperial State Crown, are actually spinels. These were once known as "Balas rubies". The quality of a ruby is determined by its color, cut, and clarity, which, along with carat weight, affect its value. The brightest and most valuable ...

6. Carat (mass) - Wikipedia

   en.wikipedia.org/wiki/Carat_(mass)

   The carat (ct) is a unit of mass equal to 200 mg (0.00705 oz; 0.00643 ozt), which is used for measuring gemstones and pearls. The current definition, sometimes known as the metric carat , was adopted in 1907 at the Fourth General Conference on Weights and Measures , [ 1 ] [ 2 ] and soon afterwards in many countries around the world.

7. Yogo sapphire - Wikipedia

   en.wikipedia.org/wiki/Yogo_sapphire

   A 0.43-carat (0.086 g) teardrop-shaped cornflower blue Yogo sapphire. Sapphires are a color variety of corundum, a crystalline form of aluminium oxide (Al 2 O 3). [14] Corundum is one of the hardest minerals, rating 9 on the Mohs scale. [15] Corundum gems of most colors are called sapphires, except for red ones, which are called rubies. [16]