I have been trying to polish a white thassos marble and cannot seem to get a shine. Any suggestions?

White thassos marble can be tricky to polish. One technique that works is to start polishing as you would normally polish. Normal is working the powder into a pasty consistency. Continue to work the slurry until it is totally dry. Continue to work dry until you get a shine. You can also try using a polishing powder that contains tin oxide. Tin oxide is an super fine powder and is also more expensive then the average polishing powders. Tin oxide can also be purchased in a pure form known as 99.99% tin oxide.
TIP Try mixing a small amount of oxalic acid with the tin oxide. Start with a formulation of one part of oxalic acid to three part of tin oxide. Work this mixture as described above for best results.