That's a bit of an overestimate. While there are thousands of known minerals, the number of common minerals is significantly less than 4000.

Here's a breakdown:

* Over 5,000 minerals are officially recognized: The International Mineralogical Association (IMA) currently lists over 5,000 minerals as officially recognized. This number is constantly growing as new discoveries are made.

* Common minerals are much fewer: Only a few hundred minerals are considered common, meaning they are found in significant quantities and are relatively widespread.

* Rock-forming minerals are even fewer: The minerals that make up most of the rocks on Earth are even more limited. There are only about a dozen major rock-forming minerals.

So, while the total number of minerals is impressive, the number of common minerals is much smaller.