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The source of obsidian for cultures inhabiting the territory of and around Greece was the island of Milos; the Starčevo–Körös–Criș culture obtained obsidian from sources in Hungary and Slovakia, while the Cardium-Impresso cultural complex acquired obsidian from the island outcrops of the central Mediterranean.
As the distribution of obsidian sources in Mesoamerica is generally limited, many areas and sites lacked a local obsidian source or direct access to one. As a result, tool curation through edge-rejuvenation and/or resharpening was commonly used on larger-mass tools, such as bifaces, to prolong the tool's (and the raw material's) utility. While ...
This is a list of sources of light, the visible part of the electromagnetic spectrum.Light sources produce photons from another energy source, such as heat, chemical reactions, or conversion of mass or a different frequency of electromagnetic energy, and include light bulbs and stars like the Sun. Reflectors (such as the moon, cat's eyes, and mirrors) do not actually produce the light that ...
Magma rich in silica and poor in dissolved water is most easily cooled rapidly enough to form volcanic glass. As a result, rhyolite magmas, which are high in silica, can produce tephra composed entirely of volcanic glass and may also form glassy lava flows. [2] Ash-flow tuffs typically consist of countless microscopic shards of volcanic glass. [3]
Opal was rare and very valuable in antiquity. In Europe, it was a gem prized by royalty. [19] [20] Until the opening of vast deposits in Australia in the 19th century the only known source was Červenica beyond the Roman frontier in Slovakia. [21] Opal is the national gemstone of Australia. [22]
Trachyte (/ ˈ t r eɪ k aɪ t, ˈ t r æ k-/) is an extrusive igneous rock composed mostly of alkali feldspar.It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, [1] and is formed by the rapid cooling of lava (or shallow intrusions) enriched with silica and alkali metals.
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).
Earthshine – Light reflected from the Earth; Zodiacal light – Faint solar glow caused by interplanetary dust at sunset and sunrise; Gegenschein – Optical effect of interplanetary dust reflections; Reflection nebula – Clouds of interstellar dust which reflect the light of nearby stars