National Gemstone

Many people may be familiar with national flowers (also known as floral emblems) and national birds, but today I will show you national gemstones.

National gemstones are stones that symbolizes the countries, and a national gemstone in Japan is a crystal.

The reason is because that once high-quality crystals were able to be extracted in Japan, and we had an excellent crystal polishing technique.

Basically, stones that are known as specialties become the national gemstones.

For example, the national gemstone in; India and Arab is a pearl, Austria and Australia is an opal, Thailand and Myanmar is a ruby, and Colombia is an emerald.

There are also many exceptions, e.g., the national gemstone in; the US is a sapphire, the UK is a diamond, and China is a jade, but the localities of these gemstones are not these countries.

These national gemstones were decided by the national flag color, the national image, or the trade culture.

国石

国花や国鳥に馴染みがある人は多いと思いますが、今日は国石を紹介します。

国石とはその国を象徴する石のことで、日本の場合は水晶です。

かつて良質な水晶の産地であったことと、水晶研磨技術も優れていたためです。

基本的には、名産である宝石が国籍となります。

例えば、インドやアラブは真珠、オーストリアやオーストラリアはオパール、タイやミャンマーはルビー、コロンビアはエメラルドです。

例外も多く存在し、アメリカはサファイア、イギリスはダイヤモンド、中国はヒスイですが、いずれも産地とは関係がありません。

これらは国旗の色や国のイメージ、交易文化などに起因しています。

• Many people may be familiar with national flowers (also known as floral emblems) and national birds, but today I will show you national gemstones.
• Many people may be familiar with national flowers (also known as floral emblems) and national birds, but today I will show you national gemstones.

  This is fine, but "today I will talk about national gemstones" or "today I will tell you about national gemstones" might sound more natural.

• National gemstones are stones that symbolizes the countries, and a national gemstone in Japan is a crystal.
• National gemstones are stones that symbolize countries, and the national gemstone in Japan is a crystal.

  One stone symbolizes. Many stones symbolize.
  
  Because you're talking about one specific thing, you would say "the national gemstone" instead of "a national gemstone".

• The reason is because that once high-quality crystals were able to be extracted in Japan, and we had an excellent crystal polishing technique.
• The reason is because that once high-quality crystals were able to be extracted in Japan, and we had an excellent crystal polishing technique.

  "Because" and "that" basically mean the same thing in this sentence, so you only need one. Either one works, but "The reason is that..." sounds the most natural to me.

• Basically, stones that are known as specialties become the national gemstones.
• Basically, stones that are known as specialties become the national gemstones.

  What you wrote is OK, but this sounds more natural to me.

• For example, the national gemstone in; India and Arab is a pearl, Austria and Australia is an opal, Thailand and Myanmar is a ruby, and Colombia is an emerald.
• For example, the national gemstone in India and Arab (?) is a pearl, Austria and Australia is an opal, Thailand and Myanmar is a ruby, and Colombia is an emerald.

  The semicolon (;) isn't needed.
  
  "Arab" is an ethnicity or regional description in English, so I'm not sure what country it is. Maybe the United Arab Emirates (the UAE)?

• g., the national gemstone in; the US is a sapphire, the UK is a diamond, and China is a jade, but the localities of these gemstones are not these countries.
• g., the national gemstone in the US is a sapphire, the UK is a diamond, and China is a jade, but these gemstones are not native to these countries.

  Same as before, the semicolon isn't needed. The last part of the sentence is understandable but sounds awkward.

• These national gemstones were decided by the national flag color, the national image, or the trade culture.
• This sentence is perfect! No correction needed!

Well written! Just some hitches here and there

• The reason is because that once high-quality crystals were able to be extracted in Japan, and we had an excellent crystal polishing technique.
• The reason is that once high-quality crystals were able to be extracted (or: were mined) (only) in Japan, and we had an excellent crystal polishing technique.

• For example, the national gemstone in; India and Arab is a pearl, Austria and Australia is an opal, Thailand and Myanmar is a ruby, and Colombia is an emerald.
• For example, the national gemstone in India and (some) Arab countries is a pearl, Austria and Australia is an opal, Thailand and Myanmar is a ruby, and Colombia is an emerald.

Interesting! Crystals play a big role in a "Final Fantasy" games as well.

• National gemstones are stones that symbolizes the countries, and a national gemstone in Japan is a crystal.
• National gemstones are stones that symbolize the countries, and the national gemstone of Japan is crystal.

• The reason is because that once high-quality crystals were able to be extracted in Japan, and we had an excellent crystal polishing technique.
• The reason is that formerly(in the past), high-quality crystals were extracted in Japan, and we had an excellent crystal polishing technique.

面白い投稿です：）