Trudy, make sure that your torch is completely full of Butane, those little cooksons torches hate even being half empty.
Make sure the little hole is wide open, this will allow more air in the mix raising the temperature.
You should have no problems soldering something so fine, should heat up terribly quickly. Make sure also that the hottest part of the flame is 1 to 2 cm away from the surface of the silver. Also perch the piece on a couple of two penny pieces so the block doesn't sap away all the heat, with a gap in between the coins.
Good luck.
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