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Hematite (/ ˈ h iː m ə ˌ t aɪ t, ˈ h ɛ m ə-/), also spelled as haematite, is a common iron oxide compound with the formula, Fe 2 O 3 and is widely found in rocks and soils. [6] Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe 2 O 3. It has the same crystal structure as corundum ...
Asterism on the surface of a blue star sapphire. A purple-pink star sapphire displaying asterism in a platinum ring.. An asterism (from Ancient Greek ἀστήρ (astḗr) 'star' and -ism) is a star-shaped concentration of light reflected or refracted from a gemstone.
A rough specimen of bloodstone. Heliotropes (from Ancient Greek ἥλιος (hḗlios) 'sun' and τρέπειν (trépein) 'to turn') (also called ematille, Indian bloodstones, or simply bloodstones) are aggregate minerals, and cryptocrystalline mixture of quartz that occurs mostly as jasper or sometimes as chalcedony (translucent).
Aphthitalite is a potassium sulfate mineral with the chemical formula: (K,Na) 3 Na(SO 4) 2.. It was first described in 1835 for an occurrence on Mount Vesuvius, Italy.The name is from the Greek άφθητος, "unalterable", and άλας, "salt", for its stability in air. [2]
The Greek and Latin names derive from the name of the river Achates (the modern Dirillo) in Sicily where this stone was first found (Theophrastus, "De lapid.", 38; Pliny, "Hist. nat.", 37, liv). The banded agate belongs to the silex family ( chalcedony species) and is formed by deposits of siliceous beds in hollows of rocks.
All colours of Greek black-red vase painting are produced by the different concentrations of iron in the clay, and the different degrees to which that iron is oxidised during firing. Iron has the special feature of forming oxides of various colours, including grey Iron(II) oxide (FeO), red Iron(III) oxide (Fe 2 O 3), and deep black magnetite ...
Limonite is named for the Ancient Greek word λειμών (leimṓn [leː.mɔ̌ːn]), meaning "wet meadow", or λίμνη (límnē), meaning "marshy lake", as an allusion to its occurrence as bog iron ore in meadows and marshes. [6] In its brown form, it is sometimes called brown hematite [7] or brown iron ore. [8]
One of the earliest known references to lodestone's magnetic properties was made by 6th century BC Greek philosopher Thales of Miletus, [12] whom the ancient Greeks credited with discovering lodestone's attraction to iron and other lodestones. [13] The name magnet may come from lodestones found in Magnesia, Anatolia. [14]