Number + 块 + Noun
块 (kuài) is a measure word (classifier) used for pieces, chunks, or blocks of something. It is placed between a number and a noun, as in 一块岩石 (a piece of rock). It is also used for items like money (一块钱), soap, and land.
桌子上放着一块蛋糕,看起来很好吃。
Zhuōzi shàng fàng zhe yī kuài dàngāo, kàn qǐlái hěn hǎochī.
There is a piece of cake on the table — it looks delicious.
他在河边捡了一块漂亮的石头。
Tā zài hé biān jiǎn le yī kuài piàoliang de shítou.
He picked up a beautiful stone by the river.
这块布料的质量很不错。
Zhè kuài bùliào de zhìliàng hěn búcuò.
The quality of this piece of fabric is quite good.