Abstract properties have no implementation and are fully abstract. They can be virtual. It should not be private and if one accessor is abstract all others must be abstract. The following is an example of the abstract property and how to use it:

// Abstract property in abstract class.
// The property is an int type that has a get and
// set method
[<AbstractClass>]
type AbstractBase() =
   abstract Property1 : int with get, set

// Implementation of the abstract property
type Derived1() =
   inherit AbstractBase()
   let mutable value = 10
   override this.Property1 with get() = value and set(v : int) = value 
   <- v

// A type with a "virtual" property.
type Base1() =
   let mutable value = 10
   abstract Property1 : int with get, set
   default this.Property1 with get() = value and set(v : int) = value 
   <- v

// A derived type that overrides the virtual property
type Derived2() =
   inherit Base1()
   let mutable value2 = 11
   override this.Property1 with get() = value2 and set(v) = value2 <- v