Here's why:
* Rarity: Tanzanite is a relatively rare gemstone, found only in one location in the world (Tanzania).
* Color: Tanzanite's unique blue-violet color is highly desirable and sought after.
* Supply and Demand: The limited supply of tanzanite coupled with high demand contributes to its higher price.
However, the price of both gemstones varies significantly depending on:
* Carat weight: Larger gemstones are more expensive.
* Color: Deep, rich colors are more valuable.
* Clarity: Gemstones with fewer inclusions (flaws) are more valuable.
* Cut: A well-cut gemstone enhances its brilliance and increases its price.
Therefore, it's impossible to give a definitive answer without knowing the specific characteristics of the sapphire and tanzanite in question.