Golf ball

1. A golf ball comprising:

a core, and

a cover,

wherein the core is formed of a material molded under heat from a rubber composition,

the rubber composition including components (Al through (Cl, where the components (A) through (C) are

(A) a base rubber,

(B) an organic peroxide, and

(C) a metal salt hydrate.

2. The golf ball as claimed in claim 1 , wherein a moisture content of (C) the metal salt hydrate in a molecular formula thereof is 6% by mass or more.

3. The golf ball as claimed in claim 1 , wherein a dissociation rate of water of (C) the metal salt hydrate in a case of heating (C) the metal salt hydrate up to 155° C. is 60% by mass or more.

4. The golf ball as claimed in claim 1 , wherein a JIS-C hardness difference obtained by subtracting a center hardness of the core from a surface hardness, of the core is 20 or more.

5. The golf ball as, claimed in claim 1 , wherein (A) the rubber composition further includes 0.1 parts by mass or more and 5 parts by mass or less of an organosulfer compound per 100 parts by mass of the base rubber.

6. The golf ball as claimed in claim 1 , wherein a metal salt of (C) the metal salt hydrate is an inorganic compound.

7. The golf ball as claimed in claim 1 , wherein one or more selected from the group consisting of calcium sulfate 0.5-hydrate, calcium sulfate dihydrate, aluminum sulfate 14-18-hydrate, magnesium sulfate heptahydrate, beryllium sulfate tetrahydrate, zirconium sulfate tetrahydrate, manganese sulfate pentahydrate, iron sulfate heptahydrate, cobalt sulfate heptahydrate, nickel sulfate hexahydrate, cupric sulfate pentahydrate, zinc sulfate heptahydrate, cadmium sulfate octahydrate, indium sulfate nonahydrate, and zinc sulfate dihydrate are used as (C) the metal salt hydrate.