If imitation is the sincerest form of flattery, then Whitby jet must be a very desirable material indeed. I can think of perhaps 20-30 different materials, both natural and synthetic, which, at one stage or another over the years, have been described as Whitby jet. In the height of the Victorian jet boom, demand for rough Whitby Jet was beginning to outstrip supply and other options were needed. The main attraction of Whitby Jet as a gem material was of course its deep black colour and liquid like lustre but more importantly its low SG 1.2-1.3. It was fine to look weighed down by the convictions of your expression of mourning, but in reality, it helped if the 7 strings of beads that you were wearing to denote you were the seventh daughter of a deceased father didn’t weigh more than a few ounces. To be a convincing simulant of Whitby Jet therefore, the imitation material would need to be light in weight. Whitby jet is also a poor thermal conductor and therefore always feels warm as heat is not quickly transferred away from the surface. Today of course we often describe jet as feeling plasticky, however in mid C19th plastic was yet to be discovered. The simulant therefore needed to be light in weight, black in colour and a poor conductor of heat.