What are the catholic necklaces called but ther not rosarys?

I'm not sure whether you're referring to Miraculous Medals or scapulars.

Miraculous Medals are round, flat pieces of metal worn on chains, and they have an image of the Blessed Mother on them with the inscription, "O Mary, conceived without sin, pray for us who have recourse to thee." These medals, having been blessed by a priest, are instruments of God's grace and power, and God often works miracles through them.

Scapulars are brown pieces of cloth string with two small squares of the same material on opposite ends of the circle of string, and the squares often have religious pictures on them. These scapulars were given to mankind by the Blessed Mother with the promise that whoever wore them willingly would be spared from Hell.