The plateau of Serabit falls away abruptly on its southern and western edge, and the stratum here appears which anciently yielded turquoise. The wish to control access to this turquoise no doubt originally led to the permanent occupation of the caves, and we shall probably not be far wrong if we imagine this in the possession of a clan or hereditary priesthood, who, in return for offerings brought to their cave, gave turquoise or the permission to work it inside the appropriated area. The offerings brought to the cave naturally led to a sacrifice and feast which, in the course of time, would hallow the precincts of the place. Prof. Robertson Smith remarked that almost every sacred site in Palestine had its cavern or grotto which served to store the vessels and utensils that were used at the sacrifice that took place near it. No religious significance originally attached to the cave. But the holiness of the sacrifice reflected on it, and in the course of time it was identified as the abode of the divinity.[22] The plateau in front of the caves at Serabit served as a High Place of Burning. Such high places were in use in Canaan before and after the Exodus. Prof. Robertson Smith showed how the barren and unfrequented hill top would be one of the most natural places chosen for the holocaust, and in this connection recalled the proposed sacrifice of Isaac on the mountain.[23] We read in the history of Samuel how he was called upon to sanctify the sacrifice on the height, of which the people would not partake until it had received his blessing (1 Sam. ix. 12); also that Solomon visited Gibeon, where he burnt sacrificial flesh and offered a thousand burnt offerings upon the altar (1 Kings iii. 4). In consequence of the building of the Temple at Jerusalem efforts were made to draw to it all the offerings, but the High Places seem to have continued till the Captivity. They finally came under the ban of the ceremonial law.[24]