Ancient Egyptian obelisks are tapering stone pillars which have a square cross-section, and which are believed to have had religious, socio-political and ornamental functions. Some weigh more than 400 tons.They appear to have been 'carved' from solid granite using a method which leaves characteristic and regular 'scallop' marks on their surface.
Although many of the quarry sites have been found to feature round stone tools made from dolerite (harder than granite) “[…] no scientific explanation of these scalloped cut marks has ever been published.”
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Also see: The Pyramids - construction