Yellow quartz ?

I have a small bag of stones I love and take most places with me, but I've never spent much time studying different crystals and stones. Over a year ago I bought a 2.5 inch lemon shaped yellow stone from someone who collects rocks and makes jewelry. It's not exactly a crystal, but I just adore it -- It has it's own glass house looking out the east window, and it glitters and glows in the sunlight.

Someone told me recently it might fade in the sunlight? I'm not sure what it is, a yellow quartz maybe? It might look a little oranger in the picture than it is, and the underside is paler than the top. I was wondering if anyone knew what it was and if it really will fade if I keep it there. In any event, thanks for looking at my humble little rock.

Pretty
It doesn't look like quartz. I wonder how heavy it is...
That might give a clue.

This site gives example of stones by color I looked through the yellow stones and don't see anything similar. You might try the gold or orange color groups.

http://www.crystalvaults.com/yellow-explained?p=1

Good luck!
Let us know if you find it!

Reminds me of calcite or alabaster (often the same thing). Nice glass box!

It's lovely, makes me want to hug it, whatever it is.
Could be a milky type of quartz.

Thanks everyone - yeah, I'm the crazy one with a rock in a glass box. So many examples online are tumbled or polished so that's makes it harder to tell. I did notice the yellow runes on Starri Knyte's link ---- why have runes when you can have yellow runes! marvelous

It's fairly heavy for it's size and I saw somewhere calcite might react to vinegar... this doesn't seem to but I don't really know what I'm doing I'm going to keep searching around because I'm really curious now.

Maybe it's sandstone?

I googled 'yellow rock' and then 'yellow stone'. The national park came up for the second query and the yellow color of the rocks in Montana is how it came to get its name. Sandstone can be worn to look quite smooth (smooth like a river rock).

Adventurine? The close up pictures on this site look a lot like it, if I knew how to make my phone take a picture that up-close. http://www.gemsbymail.com/Aventurine-Yellow-5-LB-p476.html