Salary
Average Salary: $40,000
Expected Lifetime Earnings: $1,669,920
Most gemologists who work in retail, either in sales or as an appraiser, make only around $40,000-45,000 a year (source). That's not enough to be able to afford the big stuff.
Of course, you could get lucky and make twice that if you become a jeweler to the stars, selling and designing jewels for Beyoncé.
The starting salary to work in a jewelry store is a depressingly low $21,000 a year (source). There are way more jobs at stores in the mall than there are appraisal spots open at Harry Winston's or the Louvre. Diamond cutters don't have it much better; their average take home pay is only $29,000 (source).
Like all industries, the jewelry one is directly impacted by the economy—but since jewelry is a luxury item, it's the first thing that people stop buying when money is tight. If the economy's taken a nose dive, or if you live in an economically-depressed area where folks are worrying about being able to buy food and soap, then your salary will be on the low end (if you can find work at all).
On the flip side, if the economy's doing well and lots of people want to get married, your salary will reflect that. It'll also reflect your position in the gemology world; a high-end appraiser who works for an auction or museum can make $50,000-$65,000 (source).
You could also work in a lab for GIA, where you would examine and grade stones and write reports for the jewelry industry. You'll have much better luck getting a job there if you also have an advanced degree in geology or chemistry. Salaries working in a lab range from $40,000-$65,000 (source), so again, geology and gems must be your passion. It sounds strange to say, but gemstones won't make you rich.
Not in this way at least.