Green Tourmaline strengthens Mercury and is hence, the rashi ratna for Gemini ('Mithuna'), Virgo ('Kanya').Tourmaline can be worn by those who are ruled by Saturn or Mercury.Tourmaline can also be worn by those who are looking detoxification and relieving depression It helps us to protect from radiation to purification to healing skins disorders.
Tourmaline prices can be all over the spectrum and it really depends on the color, quality, size and often from where it came from. See the link below to sold Auctions on eBay for Tourmaline specimens. As far as the Nugget is concerned, I would advise taking it to a professional Jeweler, a Gold/Silver/Platinum Buyer or even a Pawn Shop to have it tested. They should be able to tell you if if is Platinum or Silver fairly quickly.
Sorry, I don't have pics of my' Gem finds and it would take some time to gather them together for me to take pics as they are scattered all over the house and two garages!
Green Tourmaline, also known as Verdelite, is perhaps Nature's best healing crystal of the physical heart, channeling its electrical energies into the center of one's being and creating a flow of wholesome energy to all parts of the body and self.