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...aluminium cause the dark coloration of smoky quartz when the crystal has been exposed to natural radioactivity (Figure 7b). The reason for the pink colour in rose quartz (Figure 7c) is not fully understood; titanium or manganese may be involved, as may minute fibrous crystals of a complex mineral within the quartz. Figure 7 Some coloured varieties of quartz: (a) purple...

...cast their eyes towards robots as a possible source of compliant and cheaper help. The robots already in production, Belpaeme tells me, are principally geared to monitoring the elderly and infirm, or providing companionship while, as yet, performing only the most straightforward of physical tasks. Wait… companionship? “Yes,” says Belpaeme, deadpan, “Of course it...

...sand or volcanic ash. From these tracks it is possible to measure the foot length and the length of the stride. These measurements can be used to estimate both the height of the person who made the footprint and also whether the person was walking or running by using the following three formulas: Note that no units have been included in these formulas, so it is important...