Final answer:
The larger of two stones of the same quality is typically more valuable due to rarity and demand, with extraterrestrial stones being valuable scientifically, especially when found or preserved in pristine condition. In extreme cases, an exceedingly large stone could surpass standard valuations, becoming invaluable.
Step-by-step explanation:
In the context of stones or gems of the same quality (same color, cut, and clarity), the larger stone will almost always be more valuable. This is because larger stones are rarer and more sought after for their impressive appearance and potential for statement-making jewelry pieces. However, it is important to note that rarity alone does not dictate value. For example, stones that are extraterrestrial in origin, like meteorites, have scientific value that can exceed their market value as gemstones. These scientifically valuable stones are particularly valuable when collected shortly after their fall or when they are preserved in pristine condition, as with Antarctic samples. In a hypothetical scenario where a diamond is so large that it surpasses all known diamonds in quantity, its mere size would disrupt the market, and the usual valuation rules would not apply. Such an immense diamond would be practically invaluable due to its uniqueness and the lack of a comparative market.