There are 14 Regular gas price reports in the past 5 days in Mankato, MN. The average Regular gas price in Mankato, MN is $2.39, which is $0.37 lower than U.S. national average Regular gas price $2.76.
Jewelery appreciates in value over time based on increasing demand for jewelery, because there are more people to buy it. (The world's population increases every century, for example.) In order to achieve the highest appreciation for jewelery over time, it's wisest to invest in the highest-quality stones, metal and designers.
On the off chance you do have gem quality garnets (which is entirely possible, as I haven't seen them), they could be worth something on the order of hundreds of dollars, not thousands like a ruby or somesuch would be. If you know of a jeweler, couldn't hurt to take them in to check out.