The words psammite, samite sound the same but have different meanings and spellings. Why do psammite, samite sound the same even though they are completely different words?
The answer is simple: psammite, samite are homophones of the English language.
Any sandstone, but most often a metamorphosed rock unit with a dominantly sandstone protolith.
A heavy silk fabric, often interwoven with gold or silver, worn in the Middle Ages.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").