You can spend an exorbitant amount of money designing the perfect brochure to give to a customer. IBM once upon a time spent millions of dollars to create paper literature to sell their mainframe servers. Millions of dollars for a brochure that they new was only being given to 10 potential customers.
Please don't take the same approach with writing copy for your website. Don't get me wrong, you do need a well written website, but it does not have to be perfect. Every page of your website should be limited to 500 words or less. Actually 250 to 350 is probably a good measure, and you should try to have some copy on every page or your site.
Compose your copy for a high school junior or senior level education, not because your customers are uneducated, but because that level of reading can be fast and easily understood. If you need to use lexicon from your industry then you need to explain it. For example, how many people understand what "fire and brilliance" refer to unless they have shopped for, or already owned highly graded diamonds?
Remove confusion by educating your customer with everything your write, and they will reward you with a purchase or a visit to your store. They will also bestow trust upon you the same way most of us had an unbreakable trust in our favorite school teachers.
Some people might have heard that you should write your copy to include keyword phrases over and over again on the same page.
"This is a great diamond ring. We sell loose diamonds in our store. We are diamond experts. Come in and learn about the 4C's of diamonds."
We get the point, you sell diamonds. But we also are immediately fed up with your repetitiveness. Worse yet, Google will not like you either and when someone in your neighborhood searches for "Diamonds" you will be lucky to show up in the results.
Casual conversation is the best approach. But also realize that whatever you write initially will not be set in stone. Write your copy, put it on the website. Wait. Does your website show up when searching for your keyword phrases? No? Then go back and rewrite, then wait again. Any sales yet? No? Then go back and rewrite it again.
The copy re-writing process only ends when you are #1 in Google. STOP once you get to #1 for your chosen keyword phrase. Oh, and please use a single page to describe each individual service you provide. Your page for "great diamond ring" needs to focus on what makes that ring so great. Google will reward you by putting that page in the results for "great diamond ring." Want to educate about the 4C's? Then have at least 1 page dedicated to them, or even 1 page for each.
The only exception to the above described rewriting process is when you are making a blog post or publishing an article on a specific topic. Blogs and articles are designed to attract the attention and demonstrate expertise in your field. On the other hand, your website needs to sell. You need to keep rewriting your website until it creates sales or increases foot traffic.
The best person to write the copy for your website is you. The only person who truly knows what should be said on your website is the owner of the store. Of course you could ask different employees to contribute information on specific topics, but in the end someone needs to pay attention to your search engine results and weather or not the site is effective. This is an sales tool so use it as such. If your sales tool is not working, change it. Please don't hire someone to be your webmaster and expect them to write all your copy. Unless they are a retired jewelry store owner they will never understand the full scope of running the business and where you want to drive it.
Many business owners do not have the time to get this deeply involved in maintaining their website. Unfortunately that usually leads to an ineffective website. Many jewelry store owners still do not understand the difference between working "in" their business rather than "on" their business. Overseeing everyone's assigned task, and insuring that everything is running smoothly, and looking for new ways to increase revenue are examples of "on the business." But if you are working "in your business" if you are entering the sales receipts in QuickBooks, ordering inventory, making the employee schedule and working as your own bench jeweler; you might find yourself trapped, and that needs to change if you are to survive.