Teenage Space Vampires (1999) on Netflix

Plot summary

Everyone in Knollwood assumes Bill has watched one too many science fiction films when he says a UFO came down in the storm the night before. Then a windowless metal dish with gargoyles on either side appears in the vacant lot next to Mr Danvers' house, and a team of SETI specialists sets up equipment at the old observatory. Residents begin to show two small holes on their necks and to behave strangely. Hank, one of the researchers, finds a hot spot on his geothermal scanner, and Bill recognizes it as the old mine shaft. Local legend holds that coal miners found the world's largest diamond there in the 1800s, called it the Light of the Moon, and lost it while carrying it to New York.