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The Secrets of Triangles. Appearance. hide. First edition. The Secrets of Triangles: A Mathematical Journey is a popular mathematics book on the geometry of triangles. It was written by Alfred S. Posamentier and Ingmar Lehmann [ de], and published in 2012 by Prometheus Books .
Hope Diamond. The Hope Diamond is a 45.52 carats (9.104 g; 0.3211 oz) diamond that has been famed for its great size since the 18th century. Extracted in the 17th century from the Kollur Mine in Guntur, India, [1] [2] the Hope Diamond is a blue diamond. Its exceptional size has revealed new information about the formation of diamonds.
In geometry, the ten-of-diamonds decahedron is a space-filling polyhedron with 10 faces, 2 opposite rhombi with orthogonal major axes, connected by 8 identical isosceles triangle faces. Although it is convex, it is not a Johnson solid because its faces are not composed entirely of regular polygons. Michael Goldberg named it after a playing card ...
Blood diamonds (also called conflict diamonds, brown diamonds, hot diamonds, or red diamonds) are diamonds mined in a war zone and sold to finance an insurgency, an invading army's war efforts, terrorism, or a warlord's activity. The term is used to highlight the negative consequences of the diamond trade in certain areas, or to label an ...
Material properties of diamond. Burns above 700 °C in air. Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. It is a crystal that is transparent to opaque and which is generally isotropic (no or very weak birefringence ).
Synthetic diamond. Lab-grown diamonds of various colors grown by the high-pressure-and-temperature technique. Laboratory-grown ( LGD ), also called lab-grown diamond, [1] laboratory-created, man-made, artisan-created, artificial, synthetic, or cultured diamond, is diamond that is produced in a controlled technological process (in contrast to ...
A hexagram ( Greek) or sexagram ( Latin) is a six-pointed geometric star figure with the Schläfli symbol {6/2}, 2 {3}, or { {3}}. Since there are no true regular continuous hexagrams, the term is instead used to refer to a compound figure of two equilateral triangles. The intersection is a regular hexagon .
The Enigma machine is a cipher device developed and used in the early- to mid-20th century to protect commercial, diplomatic, and military communication. It was employed extensively by Nazi Germany during World War II, in all branches of the German military. The Enigma machine was considered so secure that it was used to encipher the most top ...