Hi Chile79. Welcome to the What-Is-It? forum. I see you figured out how to include photos in your forum-posts at TreasureNet. Thank you for the photos showing both the front and back of the button... the back is particularly important for time-dating a metal button.
The general form of your button, being a brass hollow 2-piece "domed" button, with a 6-pointed floral or geometric design on its front, and a backmark saying "Rich / Standard" tells us it was manufactured in Britain sometime between the mid-1830s to approximately the 1860s. After that time, the use of the quality-rating terms Rich and Standard in a backmark fell out of favor. "Rich" referred to the use of gold gilt (which is now called gold-plating), and "Standard" was a quality level, meaning basically normal or average quality, lower than "Superior."
I should mention, the backmark term "Standard" originated in Britain. Although it was used on some very early US-made ONE-PIECE brass button backmarks, it is very rarely seen on US-made 2-piece buttons. So, the statistical odds favor your 2-piece button being a British product.
The 6-pointed floral or geometric emblem on your button is definitely not a Military type. Therefore, how your 1830s-60s civilian British-made button came to be lost in a Chilean desert will probably remain a mystery.