In a letter (#149) to his friend Tevis Clyde Smith, probably in December 1930 he wrote:

The Weird Tale story, a short one that brought $64, was infinitely better, though marred by a clumsy style and a too melodramatic development. It carried out the theme I mentioned to you in a previous letter; the title is “The Black Stone,” and is the best attempt at bizarre literature that I have yet sold. I have a still shorter and better story, “The Thing on the Roof,” which I have not yet sent Farnsworth and which I may not send him, since he says he is stocked up. But this story is by far the best thing I have ever written and one which I am really inclined to believe approaches real literature, distantly, at least.

In October 1931 he wrote (letter #180) to Lovecraft and said:

I hope you liked the “Bal-Sagoth” yarn. As for “The Black Stone” my story appearing in the current Weird Tales, since reading it over in print, I feel rather absurd. The story sounds as if I were trying, in my feeble and blunderingly crude way, to deliberately copy your style. Your literary influence on that particular tale, while unconscious on my part, was none the less strong.

This story also was published in an Anthology (Grim Death) in the UK in 1932. Howard was made aware of this from a letter from Lovecraft. We can read Howard's reply in a letter from around December 1932 (letter #225b).:

No, I didn’t know my “Black Stone” had landed in the Not At Night anthology. I’m so far off the beaten track of literature *geographically, that I get only vague hints of what goes on in the world of pen and ink.

The Black Stone was also mentioned in a letter from Otis A. Kline to August Derleth in August 9, 1944:

August 9, 1944

Mr. August Derelith
Sauk City, Wisconsin.

Dear Derelith:

Thanks for yours of the 7th .
That preliminary sifting down to 29 titles looks to me like a good, representative collection of Bob’s work in the weird and fantastic field.
I note that you include “The Black Stone” on which book rights have already been sold. Do you think it should appear in both collections, published a year or so apart?
I don’t have any further suggestions or deletions at this time, but wondered about this item. I do agree with what you say about the Conan yarns. A steady, unbroken diet of violent action and sabre-hacking would, I think, pall on the reader.
I’ll look forward to hearing further from you on this in due course, and also to trying that additional Someone in the Dark in the reprint market when it comes in. Best regards.

Cordially,

See also: The Black Stone (early draft).