Yes, it is valuable (probably), but mainly because of its gold content, rather than as a collectable coin.
First we need to confirm if it's a sovereign or half-sovereign. A sovereign is slightly smaller than an Australian 10 cent piece; the half-sovereign is about the size of the 5 cents.
Second, the picture is too blurry to confirm whether or not it bears a mintmark. London-minted coins don't have a mintmark, whereas colonial-minted coins do. The mintmark would be a tiny letter on the ground-line, above the date. Australian-minted coins can be worth slightly more.
At current gold prices, a sovereign contains about AU$1750 worth of gold; a half-sovereign is half of that.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis