According to Sinkankas and Miller in the Standard Catalog of Gem Values, 2nd. Ed. the prices for rubies are dependent on origin, color, size, and clarity and sell for between $100 to $15,000/ ct.
Myanmar (Burma), Thailand, Sri Lanka and Tanzania are the most important sources of rubies. Others are Afghanistan, Australia, Brazil, India, Cambodia, Kenya, Madagascar, Malawi, Mozambique, Nepal, Pakistan, Zimbabwe, Tajikistan, the USA and Vietnam.
Color is the most important quality when determining a ruby’s value. The best ruby has a "pure, vibrant red to slightly purplish red color." As the color becomes "too orangy or more purplish", the ruby's value diminishes. Clarity and luster also affect the price. The more valuable a ruby is, the more brilliant and transparent it is.There is also cut and shape to consider, along with possible heat treatment to enhance the color and fracture filling with lead glass to prepare rubies with lots of flaws and imperfections for jewelry. Price of course increases greatly with size.
Luckily, rubies are durable gems. Warm soapy water and a soft cloth are enough to keep them clean.
Of interest, Canada's True North Gems recently announced that they plan to begin construction of a ruby mine in Greenland by the end of the year. The news comes after 10 long years of exploration. Find out more from The Arctic Journal.