Ruby: fluorescent magenta-red, LW

Ruby is a variety of corundum {Al2O3} and occurs in aluminum-rich metamorphosed limestone (marble) environments. The specimen in the picture has well-formed but small crystals of hexagonal cross section which are characteristic of corundum.

Rubies do not always fluoresce this brightly in long-wave UV. Such a bright FL response by a ruby gemstone often indicates synthetic origin, but in this case it's obvious the rubies are natural. These particular rubies are not gem-grade, since they are opaque and fairly small. They make for a great fluorescent specimen, though!

Note the marks in the calcite-dolomite produced by the hand-scraping that's used to expose the crystals from the matrix. Hand-scraping is the generally-accepted method of doing this and is far preferable to acid etching! A carbide scribe or hardened steel implement is usually used for hand-scraping of matrix. Some people prefer a Dremel, but this is very risky... one slip, and your crystals are ruined. (This happened to me with a nice, large andradite crystal I'd collected at Sterling Hill. I will never do that again.)
The specimen above was mined in Vietnam. It was for sale on the website of CR-Scientific last year and is now in a private collection.

Photo is shown here with permission.

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Ruby corundum photo is copyright 2003, CR-Scientific