Hi! The "dirt" is used in its plural form here, but I found it is an uncountable noun. However, I also learn that the plural form for an uncountable noun could sometimes refer to a larger category, like fruits, meaning all kinds of fruit (apple, pear etc). Could you confirm if "dirts" a mistake or a proper use?
"Products which are made from dirts and are subjected to high temperatures are known as ceramics."