BOSTON ( TheStreet) -- GT Solar ( SOLR) was one of several stocks trading below $10 and moving on above-average volume Tuesday after the solar company said a selling stockholder is offering 10 million shares of common stock.GT Solar said that the shareholder will offer the 10 million shares as well as an option for the underwriters to buy an additional 1.5 million shares of common stock to cover overallotments, if any. The selling stockholder will also sell up to 15 million additional shares to UBS Securities and one of its affiliates. GT Solar said it will not receive proceeds from the offering or sale of shares, although it will cover the stockholder's expenses. Shares GT Solar of slumped by 91 cents, or 10.4%, to $7.87. Volume topped 2.27 million shares, compared to the average daily share volume of 2.35 million. Elsewhere, IncrediMail ( MAIL) continued to rise, jumping by 58 cents, or 11.1%, to $5.80 after the company said last week that its board has approved an interim cash dividend for 2010 of 45 cents per share. IncrediMail shares have rallied more than 22% over the last three sessions. Volume topped 356,000 shares, compared to the average daily share volume of 41,000. Spherix ( SPEX) shares tumbled by 50 cents, or 27.6%, to $1.31 after the company registered Friday for a $10 million mixed securities offering. A majority of the net proceeds to fund our operations and to continue the development of D-tagatose, Spherix's proprietary low-caloric sweetener that was originally developed to treat Type 2 diabetes but is now also being explored as a potential treatment for high triglycerides. Volume topped 652,000 shares, compared to the average daily share volume of 57,000. Brooks Automation ( BRKS) dropped by 77 cents, or 11.5%, to $5.92 after Barclays Capital analyst C.J. Muse downgraded the company to equal weight from overweight. Volume topped 953,000 shares, compared to the average daily share volume of 511,000. Muse downgraded several other semiconductor equipment companies, including KLA-Tencor ( KLAC), Verigy ( VRGY)and LTX-Credence ( LTXC). -- Written by Robert Holmes in Boston. >To contact the writer of this article, click here: Robert Holmes. >To follow Robert Holmes on Twitter, go to http://twitter.com/RobTheStreet. >To submit a news tip, send an email to: firstname.lastname@example.org.