Diamonds - Marg Melanson
Diamonds have long been known as costly, precious gems. Chemically speaking, however, a diamond is the same as a hunk of coal. Diamonds are pieces of crystallized carbon that were formed in the depths of the earth eons ago and brought up to the surface by volcanic pressures. When cut into facets, the diamond is the most brilliant of all gems. It is also the hardest - so hard, in fact, that it is used in drills and other tools for cutting hard materials.
ฝึกที่คำคมนี้
แก้ไขข้อความ
หรือเพียงแค่ให้ความคิดเห็น:
