If a loved one has (or if you have) a special birthday coming up, learn how to celebrate it with the perfect jewelry gift.

What do 12, 18, 21, 25, 30, 40, 50, 60, 70 and 75 have in common? It’s not a math question. The correct answer: jewelry.

These milestone birthdays call for a special gift, and jewelry is a great option because it’s lasting and, chosen with care, has emotional meaning and sentimental value. What’s more, it’s appropriate for women and men.

If you’re about to celebrate a friend or family member’s milestone birthday, you may be considering a whole range of gift ideas, from apparel to electronics to accessories such as jewelry. Keep in mind, however, that clothing will be out of style next season and a brand-new smartphone will be a technological dinosaur in two years. Though such gifts might be appreciated, they are rarely treasured. That’s the great advantage of jewelry: It’s a lifetime reminder of the special day and the special person who gave the gift.

Is it ever too soon?

Fine jewelry is an appropriate gift for an extraordinarily wide age range. Some cultures give gold baby earrings for pierced ears before a child can walk. A more common age for a first jewelry gift is around 12, when young girls and boys are better able to care for and understand the value of fine jewelry. In fact, jewelry is often given to welcome girls and boys into the maturity that some cultures recognize at ages 12 to 15. Examples include charm bracelets, a cross necklace, gold chains (boys and girls), men’s watches and women’s watches (choose age-appropriate, durable models). Birthstone rings or other jewelry are popular, too, as girls move into their teen years and begin to express their individuality.

Young adults

When a person reaches age 18, which often coincides with high school graduation, jewelry is a common gift to recognize the achievement. A daughter often receives her first pearl necklace and a son is given his first "good" watch. These are really appropriate gifts because there's less concern about "growing out" of the jewelry than when they were younger. In addition, promise rings are popular with this age group because they can signal commitment without a proposal.

On their own

Many of the pieces mentioned up to now help build a person’s wardrobe of jewelry basics. At age 21, however, tastes develop more outwardly as people begin to purchase their own clothing without financial or other input from parents. When it’s time to choose a jewelry gift for someone in this age group, pay attention to how he or she dresses. Trendy or conservative? Bold or muted tones? White or yellow metals? Do you envision the jewelry being worn at work or play? The answers to these questions will help you narrow the choices and end up with a piece the recipient will treasure. Ideas include gold or sterling silver pendants — maybe with diamonds or gemstones — earrings for women or men, necklaces for men and women, fancier gold bracelets and, for romantically inclined couples, a heart necklace, couple rings and promise rings.

And if you’re hoping to receive jewelry yourself, it’s time to start dropping hints about what you like. Point out jewelry and watches you see while window shopping, dining out, watching TV or looking through a magazine or website. Also check jewelers’ websites for “wish list” pages where you can list particular pieces you like, then innocently steer your friends and family to that website as your birthday nears.

As we mature

The milestone birthdays from the 30th on are times to explore and stretch as we become more experienced with jewelry and our tastes widen. Interest in color that began with a birthstone ring can blossom into a full-fledged interest in color gemstone jewelry. These stones often come with fascinating and adventurous stories of how they were mined, and that makes them even more special. Start with the three most well-known color gems, perhaps ruby earrings, a sapphire necklace or an emerald ring. Then branch out to other less well-known — but every bit as beautiful — color gems. You may want to consider a gently purple amethyst ring, light blue aquamarine necklace, opal earrings with their combination of cool white body and internal fire, a voluptuous pearl ring or any alexandrite jewelry, an interesting gem that changes from teal to magenta depending on the light.

As budgets allow, diamond jewelry is an extra-special gift. And don’t forget that diamond and gemstone jewelry is an appropriate gift for men. Earrings, necklaces and rings for men, as well as tie tacks or tie bars, often have a diamond, onyx or color gemstone accent. And for the man who enjoys making a statement at work, the gift of a French-cuff shirt with cuff links will elevate the cool factor and lend an air of authority.

Two bonus hints

For a truly special gift at any age, check with your jeweler for custom jewelry design advice. Get your creative juices flowing and come up with your own design. A good jeweler will be able to refine your design, offer suggestions and have it made for the special day.

Size is an important consideration with jewelry. When making a selection, think about how the jewelry will look on the person wearing it. A bold ring will dwarf a small finger. A small earring on a large ear will make the ear look even bigger. And a heavy necklace will weigh down a petite torso. Just as with apparel, jewelry should be in proportion to the person wearing it.

So there you have it — if someone you love is coming up on a special birthday, you can’t use the excuse that you just didn’t know what to get! And even if it’s not a milestone birthday, you can make any birthday special with the right jewelry.