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Another old name is dichroite, a Greek word meaning "two-colored rock", a reference to cordierite's strong pleochroism. It has also been called "water-sapphire" and "Vikings' Compass" because of its usefulness in determining the direction of the sun on overcast days, the Vikings having used it for this purpose. [ 8 ]
Actinolite. Nephrite (var.); Adamite; Aegirine; Afghanite; Agrellite; Algodonite; Alunite; Amblygonite; Analcime; Anatase; Andalusite. Chiastolite; Andesine ...
The Oxford English Dictionary suggests an alteration of Anglo–Norman pedoretés (classical Latin pæderot-), a kind of opal, rather than the Arabic word faridat, meaning "gemstone". The Middle English Dictionary ' s entry on peridot includes several variations: peridod, peritot, pelidod and pilidod — other variants substitute y for letter i ...
Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel. Its color is normally apple-green, but varies from turquoise-like cyan to deep green. The darker varieties of chrysoprase are also referred to as prase.
The globe shows an enlarged Eurasian continent and an empty ocean between Europe and Asia. The mythical Saint Brendan's Island is included. Cipangu ( Japanese archipelago ) is oversized and well south of its true position; Martellus 's map is followed in developing an enormous phantom peninsula east of the Golden Chersonese ( Malay Peninsula ).
Jasper breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals, and snuff boxes. The density of jasper is typically 2.5 to 2.9 g/cm 3. [4] Jaspillite is a banded-iron-formation rock that often has distinctive bands of jasper.
A 17th century English lapidary text. The etymological root of the word lapidary is the Latin word lapis, meaning "stone". [6] In the 14th century, the term evolved from lapidarius, meaning 'stonecutter' or 'working with stone', into the Old French word lapidaire, meaning 'one skilled in working with precious stones'.
Grossular is a calcium-aluminium species of the garnet group of minerals.It has the chemical formula of Ca 3 Al 2 (SiO 4) 3 but the calcium may, in part, be replaced by ferrous iron and the aluminium by ferric iron.