The Magic of Reality by Richard Dawkinsを図書館から借りて読み始めました。
What are things made of?の章からの引用です。
The sand in sandstone is mostly made of
quartz and
feldspar, two common crystals in the Earth's crust.
"
quartz" は石英または水晶だと分かりますが、"
feldspar" は馴染みのない英単語なので辞書を見ます。
・Oxford English Dictionary: An abundant rock-forming mineral typically occurring as colorless or pale-colored crystals and consisting of aluminosilicates of potassium, sodium, and calcium.: Its most abundant mineral is
feldspar, which accounts for two-thirds of the Earth's crust.
この手のものは写真がないと分かりずらいので、写真のあるWikipediaを見ます。
Compositional phase diagram of the different minerals that constitute the
feldspar solid solution.
Feldspars are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight.
Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase
feldspar is known as anorthosite.
Feldspars are also found in many types of sedimentary rocks.
...
Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as a filler and extender in paint, plastics, and rubber. In glassmaking, alumina from
feldspar improves product hardness, durability, and resistance to chemical corrosion.
写真を見たい方はWikipediaの次のサイトを見て下さい。
https://en.wikipedia.org/wiki/Feldspar