Having breakfast

Danya, Thank you for a marvelous explanation!

I understand, that a focus goes into the word "tea", for this reason I can write only one "a".

"So it's a green or herbal tea."
"I need to drink a cup of green or herbal tea" Thanks!
_________________________________________

I have two queries to ask you:

1) "Now that I write about it" or "now that I am writing about it"

Are both sentences can be interchangeably used in our situation? Are both are correct?

---------------------------------------------
2) My nagging doubt about usage of the indefinite article before the word "herbal"

It's great that my teachers become from different countries and cultures.:-))))

I was searching and I found the answer by myself.
I wonder what other citizens think about that?
My results include only two countries: the United States and Great Britain.

It's all about the subtleties of sound. Language is music.

Some of the results I present below:

a) http://www.grammarphobia.com/blog/2009/09/herbal-remedies.html
 

"... If the word begins with a vowel SOUND, the article is “an” (as in “an apple,” “an hour,” “an honor,” “an herb,” “an umbrella”).

If the word begins with a consonant SOUND, the article is “a” (as in “a hotel,” “a house,” “a utopia,” “a unit,” “a university,” “a use,” “a European,” “a one-time offer,” “a once-over”).

In American English, the “h” in “herb” is not sounded; it is silent, so it’s preceded by “an.” In British English, the “h” in “herb” is sounded, so it’s preceded by “a.”

You say, “No other words with silent letters get singled out with such nonsense.” Of course they do! All words beginning with a silent “h” are preceded by “an.” ...

I’ll quote The American Heritage Dictionary of the English Language (4th ed.): “The form a is used before a word beginning with a consonant sound, regardless of its spelling (a frog, a university). The form an is used before a word beginning with a vowel sound (an orange, an hour).”

And this is from The New Fowler’s Modern English Usage, edited by Robert H. Burchfield (who uses “AmE” for American English, “BrE” for British English): “AmE herb, being pronounced with silent h, is always preceded by an, but the same word in BrE, being pronounced with an aspirated h, by a.”

AmE an herbal tea
BrE a herbal tea

b) http://en.wikipedia.org/wiki/Herbal#cite_note-1

^ The use of a or an depends on whether or not herbal is pronounced with a silent h.
 

c) http://www.worldwidewords.org/qa/qa-anh1.htm

"...The situation is complicated by a shift that has been taking place in the pronunciation of words with initial h over the past couple of centuries. At one time, many more were said with the h silent. This explains the appearance of an in old texts where we would now use a; the classic case is that of the King James Bible, where — to take the first example out of dozens — in Genesis the text reads “And Adam lived an hundred and thirty years”. A good example is that of herb, which Americans today continue to say the way their English forefathers did, without the initial h. British English has moved on, and it is now thought uneducated for British speakers to say erb.

To complicate the matter, usage is shifting. Younger people prefer a more often in such cases in speech as well as writing. Forms like an hotel are heard from, and written by, older people in the main. I use an hotel consistently in both speech and writing, and count myself old-fashioned as a result. The form an heraldic you mention is by no means unknown, though it is less common than the others, but that may just be because we have less cause to use the phrase than ones like an hotel..."

d) http://www.thefreedictionary.com/herbal - pronunciation [wymowa]