Correct usage of pronoun: "their" vs "its" [closed]

Solution 1:

In the sentence you gave, their is correct. The antecedent of the underlined pronoun is the stones, which is a plural noun phrase. Therefore the correct statement is:

The stones are small, but their value is great.

Solution 2:

I think JSBangs's answer is probably correct, but I wanted to clarify that in some cases it may be incorrect, depending on the context. It depends what the pronoun "it" is meant to refer to. If "it" refers to the stones, then it should be "they" since there are multiple stones. However, consider the following:

The ring was quite impressive, solid gold with many fine rubies. The stones were small, but its value was great because of its age.

In this example "the stones" refers to the rubies, which are small, but the ring is nevertheless still valuable. In this example "it" refers to the ring and it using "their" instead would change the meaning of the sentence. So depending on the context, either word might be correct.