It's found in wolframite, and hubnerite and so on; but this is calcium tungstate, where it is found in connection with lime.
"Shadow Mountain"
Dane Coolidge
I also found that this tungstate could be put into a vacuum chamber of glass and fused to the inner walls of the chamber; and if the X-ray electrodes were let into the glass chamber and a proper vacuum was attained, you could get a fluorescent lamp of several candle-power.
"Edison, His Life and Inventions"
Frank Lewis Dyer and Thomas Commerford Martin
Your statement regarding the action of the oxides of gold, in combination with the tungstate of bdellium, has more than in practice verified itself.
"The-Brick-Moon-and-Other-Stories"
Hale, Edward Everett