Learning F# – BlackJack

This source code will serve as a reference for common set operations that have been partially implemented for a BlackJack game.
Feedback is welcomed within the comments section as I continue learning this mythical language.

module Core
 
type Suit = | Spades
            | Clubs
            | Diamonds
            | Hearts
 
type Face = | Two | Three | Four | Five 
            | Six | Seven | Eight | Nine | Ten
            | Jack | Queen | King | Ace
 
type Card = {Face:Face; Suit:Suit}
 
type Deal = | Hand of Card * Card
            | Hit of Card
 
let private suits = [Spades; Clubs; Diamonds ; Hearts]
let private faces = [Two; Three; Four; Five; Six; Seven; Eight; Nine; Ten;
                     Jack; Queen; King; Ace]
 
let deck = [for suit in suits do
            for face in faces do
                yield {Face=face; Suit=suit}]
 
let hitPlayer (deck:Card list) =
    (deck.Head, deck.Tail)
 
let deal = function
    | card1::card2::remaining -> Some(card1, card2), remaining
    | _ -> None, []
    
let shuffle xs =
    let swap i j (array : _[]) =
        let tmp = array.[i]
        array.[i] <- array.[j]
        array.[j] <- tmp
    let rnd = System.Random()
    let xArray = Seq.toArray xs
    let n = Array.length xArray
    for i in [0..(n-2)] do
        let j = rnd.Next(i, n-1)
        swap i j xArray
    xArray |> Seq.toList
 
let hand, deckRemaining = deal (shuffle deck);;
let cardsLeft = Seq.length deckRemaining;;