Diamonds are hot this summer and prices have shot up by 20 to 30 percent in recent weeks as more people have decided to invest in stones larger than one carat. And with advertisements for diamonds proclaiming "a diamond lasts forever", the classic styles continue to be the most popular.

Zhu Yun, chief product officer of I DO, and Chen Xinyi, chief product officer of M&L, two companies that specialize in the design of diamond rings, said consumers have been setting high standards for diamond jewelry.

First of all, as more knowledge about diamonds has become available through the Internet, people have been developing new ideas about what a good diamond ring should be like.

In the past, people only paid attention to diamonds' color, carat weight and clarity, they said, but now buyers demand the best craftsmanship as well, preferring stones that are 3 EXs, which means the cutting, burnishing and polishing are all excellent.

This keener pursuit of quality jewelry may have something to do with the fact that in the capital, people are getting married later in their lives than they once did and they have savings available to spend on the best.

"We found that most of our customers buying wedding rings are older than 28. Being more economically stable, they are more particular about quality," said Zhu. "For them, cutting is most important. The more exquisite the better."

Meanwhile, people born in the 1980s and 1990s are more fond of wedding jewelry with easy-to-understand meanings.

"One of our best-selling products is a pair of rings with one half of an angel's wings on each one, meaning men and women are only angels with half wings. Only when we find each other can we fly," Zhu said.

Rings that get their inspiration from ancient stories or deep ideas are well-received among older people.

Romantic stories from ancient China and the ancient wisdom of the Eight Diagrams have been engaged into two of I DO's series named "pair ring" and "Tai Chi".

"The Tai Chi series entails a primitive and pure view of yin and yang; men and women are inside each other. The relationship is harmonious in nature," Zhu said.

While, the classic combination of platinum and diamonds continue to sell well this year as always, diamonds with gold or rose gold seem more trendy.

"We have more new series that put together gold or rose-gold with diamonds than in the past, because they have proved to be as elegant as platinum ones," Zhu said. Rose-gold is a mixture of gold, copper and silver, which is stronger and looks more reddish than pure gold.

At the same time, gold rings with decorative patterns, which have thicker and wider circles and are much heavier than traditional rings, are also popular this year.

"Although this type of European-style ring is not familiar to buyers in China, they are quickly gaining popularity," Zhu said.

In addition, compared with conventional rings that have a smooth and glossy surface, rings with textured surfaces are becoming more and more popular.

"Fiber drawing and textures of irregular patterns are the hits," said Zhu.

In addition, rings with mixed elements from both the East and West have become fashionable as evidenced by I Do's Coronation Series, which uses ruby and diamond.

"Ruby comes from Asia. When it arrived in Europe, people gave it more meanings, including power and wealth. So, in Western royal coronation ceremonies, you will always find rubies on the crowns," Zhu said.

"We got the inspiration to use diamond and ruby to make a miniature crown on our rings. It turns out that people of all ages like the design very much."

Another highlight in the design of diamond rings in recent years is to have rings with one big diamond that is dotted by a couple of shining fragmented smaller diamonds along the curve. This differs from past years when single-diamond rings dominated the market.

Although diamonds are very versatile and appeal to people of all ages and occupations, buyers still need to make choices regarding their personal style, status, occupation, age, face shape, and skin color.

"For those in the fashion industry or those who are extremely sociable, I would recommend jewelry that is large and exaggerated to enhance their creativity and uniqueness," said Chen.

"But for those in the real estate industry, financial sector and lawyers, classic combinations such as platinum and diamond are always good choices, because they can add to your preciseness and give you low-profile elegance."

Chen also said rose-gold jewelry is more suitable for fair-skinned women while platinum makes people with darker skin more beautiful. A round face looks prettier with slimmer pendants, while round, full shaped ear or necklace pendants go well with an oval face.

Additionally, Chen pointed out that diamonds need to be taken care of from time to time because they absorb oil and water from the air and can lose their gloss.

"Just a regular brush with ordinary liquid detergents is enough to keep diamonds shining," Chen said.