early European visitors saw men wearing the hei-tiki and it is probable that the squat shape of the figure was influenced by the hardness of the material and that it was later likened to an embryo and endowed with magical powers.
The shape is also probably due to the fact that tiki were often made from adze blades. Adzes and chisels made from greenstone were also prestige items and the shape of a greenstone adze lends itself to conversion into a tiki. There are several extant examples of half-finished tiki evidently originally small adzes and sometimes on completed tiki, traces of the original cutting end shaping of a adze can be seen, usually at the foot.
Tiki or heitiki are most commonly made from nephrite, a stone related to jade and found in several places in New Zealand's South Island. It is called pounamu in Maori, greenstone in New Zealand English. The Maori name for the South Island, Te Wai Pounamu, refers to this stone.
There is some variety in the forms of tiki but this variation has not been very fully studied in relation to region of origin. The head inclined left or right appears to have no particular significance. One clear variation is between tiki with the head upright and those with the head tilted sideways.