けど usage in ”魔石灯”がいい例だけど、”魔石”は…

Question

I know that けど is a colloquial form of けれども and that is used to connect two sentences with the meaning of "but, although" but in the following sentence I cannot understand its usage.

僕達のホームにあった”魔石灯”がいい例だけど、”魔石”はヒューマンの技術で加工することで色々な方面―発火装置だとか、食糧を保存する冷凍器とか―に活用できるから、貴重な資源扱いになっている

The following sentence is my translation:

The "magic stone" is used as a valuable resource, because it can be used in different fields, such as in incendiary devices, in the freezers to store the food of first necessity and a good example is the "light at the magic stone" that we had at our home.

In this sentence is it used with a different nuance?

Answer 1

This is an example of another important role of けど, けれど, が, だが, ですが, etc: to provide introductory, background information (前置き) before dealing with the main issue (本題). Any monolingual dictionary explains this usage.

From デジタル大辞泉:

２ ある事実を前置きとして述べ、本題に結びつける意を表す。「経験から言うんだ―、時間には厳しいほうがいい」「これおもしろい本だ―、君読まないか」

Examples:

• 今日は日曜日だけど、どこに行きたい？ It's Sunday, (so) where do you want to go?
• この前の話だけど、覚えてる？ Do you remember it, what we discussed the other day?
• 去年日本に行ったんだけど、楽しかったよ。 I visited Japan last year, and it was fun.

Some of these can be safely translated using but (eg 失礼ですけど = "Excuse me but ..."). In your case, you can simply translate it as if it were two separate sentences: "... is a good example. The magic stone is used as ..."