Final answer:
The gold alloy used for cast-removable partial dentures is hard, type III, which is durable and resistant to wear while still having a suitable level of hardiness and workability.
Step-by-step explanation:
The gold alloy used for cast-removable partial dentures is hard, type III. These alloys are designed to be durable and resistant to wear, which is essential for the function of partial dentures that have to withstand the forces of chewing and biting. Type III gold alloys contain high percentages of gold, along with other metals like silver, copper, and sometimes small amounts of platinum or palladium to optimize their mechanical properties and ensure a mix of hardness and workability suitable for creating partial dentures.