NEW YORK (AP) â¿¿ Shares of II-VI Inc. tumbled more than 10 percent Friday after the manufacturer cut its fiscal fourth-quarter outlook, citing the continued drop in prices of a key material that it makes, and issued a weak guidance for the upcoming fiscal year. THE SPARK: For the fiscal fourth quarter, which ends June 30, the company now expects a profit of 23 cents to 25 cents per share on $135 million to $137 million in revenue. Analysts, on average, expect a profit of 29 cents per share on $141.1 million in revenue, according to a FactSet poll. II-VI, which makes a variety of optical components, metals and chemicals, had previously predicted profit of 27 cents to 31 cents per share on $139 million to $142 million in revenue. The Saxonburg, Pa., company said late Thursday that it expects its results to increase sequentially quarter-by-quarter as the year progresses. But its forecast for the upcoming year, ending in June 2013, also fell well short of analysts' predictions. It sees profit of $1.14 to $1.21 per share, when analysts were estimating $1.36 per share. THE BIG PICTURE: II-VI said the value of its stock of tellurium, a metal it makes that's used in alloys and solar panels, has dropped because the metal's price is dropping as a result of volatility in the global solar panel market. Strong production in China and weakening demand in Europe caused too much supply of solar panels and a collapse in prices. II-VI said it expects a write-down of $1.7 million to $1.9 million, or 3 cents per share, for the current quarter on its inventory of the metal. The company's profit prediction for the full fiscal year also was well below analysts' expectations. It plans to release full results before the market opens on Aug. 2.