Looking at the universe of stocks we cover at Dividend Channel, on 5/20/15, Hecla Mining Co. (HL - Get Report), Griffon Corp. (GFF), and Schweitzer-Mauduit International, Inc. (SWM) will all trade ex-dividend for their respective upcoming dividends. Hecla Mining Co. will pay its quarterly dividend of $0.0025 on 6/1/15, Griffon Corp. will pay its annual dividend of $0.04 on 6/25/15, and Schweitzer-Mauduit International, Inc. will pay its quarterly dividend of $0.38 on 6/26/15.

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As a percentage of HL's recent stock price of $3.22, this dividend works out to approximately 0.08%, so look for shares of Hecla Mining Co. to trade 0.08% lower — all else being equal — when HL shares open for trading on 5/20/15. Similarly, investors should look for GFF to open 0.24% lower in price and for SWM to open 0.90% lower, all else being equal.

Below are dividend history charts for HL, GFF, and SWM, showing historical dividends prior to the most recent ones declared.

Hecla Mining Co. (HL - Get Report):

HL+Dividend+History+Chart

Griffon Corp. (GFF):

GFF+Dividend+History+Chart

Schweitzer-Mauduit International, Inc. (SWM):

SWM+Dividend+History+Chart

In general, dividends are not always predictable, following the ups and downs of company profits over time. Therefore, a good first due diligence step in forming an expectation of annual yield going forward, is looking at the history above, for a sense of stability over time. This can help in judging whether the most recent dividends from these companies are likely to continue. If they do continue, the current estimated yields on annualized basis would be 0.31% for Hecla Mining Co., 0.24% for Griffon Corp., and 3.59% for Schweitzer-Mauduit International, Inc..

In Monday trading, Hecla Mining Co. shares are currently off about 0.9%, Griffon Corp. shares are up about 0.7%, and Schweitzer-Mauduit International, Inc. shares are off about 0.5% on the day.