Having looked at these "ornaments"..I am of the opinion that they are made of Resin Stone,..or Stone Resin,as it is also known...this "resin" is impervious to the hot needle test,as it is a mix of resin and real stone...this item here is made of resin stone,.and it too is impervious to the hot needle test,.also see text, explaining resin stone,...as for the bit that you have that has broken off,...I,d be crushing it with a hammer..and when it turns to powder you,ll know....
"Stone Resin" is a material used by the tile industry to mimic the look of natural stone. It is used for large items like the shower tray you mention as well as various trim items. Stone resin is far cheaper to produce than if the items were made of actual stone. A shower tray of actual stone would start out as a large slab of stone and then would have to be machined and hand carved to the desired shape. The same goes for trim mouldings and accessories like soap dishes, towel bars, tissue holders, and shower shelves. In the case of intricate trim mouldings, each one would have to be hand carved.
Manufacturers are able to mimic the look of travertine, limestone, and sometimes marble or granite with resin castings. They start with a rubber mold and use a liquid resin, colored to match the desired stone, to cast the piece. Once the resin sets up, the rubber mold is peeled away leaving a finished piece. The accuracy they achieve is remarkable and the color matches are quite good.
Most resin pieces are cast in colors that match the brown, ivory, red, and yellow colors of travertine. There are also colors that mimic the greens and similar colors of limestone. There are not many resin castings that mimic marble and granite because of the translucent color and veining of the actual stone. Acceptable matches are very difficult to produce.
Some specialty trims that mimic copper, bronze, and other metals also start out as resin castings. A paper thin layer of "metallic" finish is then burnished onto the surface of the casting. This also tends to keep the price down. A piece cast in the actual metal would be extremely expensive.
An alternative to stone resin is "cast stone". The same type of items are manufactured, but a concrete slurry is used instead of resin. The result is a concrete gray casting that must then be coated with a colored finish to mimic the texture and color of the actual stone. They must be well sealed because exposure to water will severly discolor the pieces. Resin, by its' very nature, is mostly impervious to discoloration by water
