In his Autobiography, Franklin wrote: "I had brought over [to London] a few Curiosities among which the principal was a Purse made of the Asbestos, which purifies by Fire. Sir Hans Sloane heard of it, came to see me, and invited me to his House in Bloomsbury Square, where he show’d me all his Curiosities, and persuaded me to let him add that to the Number, for which he paid me handsomely." In "Conversation with Franklin" (V) (Reprinted from Adolph B. Benson, ed., Peter Kalm’s Travels in North America. The English Version of 1770 (2 vols., N.Y., 1937), pp. 157, 158, 159-60.), Peter Kalm also recalled: "Asbestos. The mountain flax, or that kind of stone…or the amiant with easily separable soft fibres, is found abundantly in Pennsylvania. Some pieces are very soft, others pretty tough. Mr. Franklin told me that twenty and some odd years ago, when he made a voyage to England, he had a little purse with him, made of the mountain flax of this country, which he presented to Sir Hans Sloane. I have likewise seen paper made of this stone…Mr. Franklin had been told by others that on exposing this mountain flax to the open air in winter, and leaving it in the cold and wet, it would grow together and become tougher and more suitable for spinning.” Sources include: Arthur MacGregor, ed., Sir Hans Sloane: Collector, Scientist, Antiquary, Founding Father of the British Museum, published by British Museum, 1994, pp. 129-30, and
Clifford Frondel, "Benjamin Franklin's purse and the early history of asbestos in the United States," Archives of Natural History 15, 1988, pp. 281-87.