It's not a kumquat! It's about the size of a ping pong ball.
Are you sure it's not a kumquat? I just bought some that were the size of ping pong balls. They were the largest and sweetest ones I've ever gotten.
Can you cut one open for further visual information? The seeds would be helpful. How do you know it's a fruit? Where did you get it?
or taste one.
My guess is that this is in fact some type of kumquat (there are dozens of cultivars) or some sort of hybrid cultivar/cross like a kalamansi (a.k.a. calamondin). The latter are a common sight in the Philippines, although these days they are showing up at some of the local farmers markets here in the SF Bay Area.
The knob is a bit unusual, but I don't think you can use that as the determining characteristic as the knob can be found in various citrus fruits like the mineola tangelo and the sumo citrus (both of which are typically larger than what you described).
A cross section of the interior would be helpful as well as how it tastes.
My other thought is that this could be some cultivar of rangpur lime. Those are typically about golf ball sized, orange and often have a knob on the bottom.
Impossible to separate the sections! Very sour. Probably a kumquat.
Well, if it's that sour, it's likely not closely related to a mineola or sumo citrus.
The fact that it doesn't segment also points to some variety of kumquat.
My revised guess is that this is an Indio mandarinquat, a kumquat-mandarin hybrid developed in California in the early Seventies and commercially grown here on a very small scale. The first photograph appears to match the description given here:
and a Google image search for "Indio mandarinquat" generates multiple images of very similar fruit (the distinctive knob or neck, the color and size).
I bought those too, at Central Market - I'll look next time I go but I am pretty sure they were SomeotherQuat. I used them as part of my fancy deboned duck stuffing but I am guessing you will not go down that road :-) also some of mine were kinda sweet and some sour. All delicious.
There are limeqats and mandarinquats. Maybe its a mineolaquat.
Looks like a calamondin to me...
No they are not actual kumquats, but a hybrid. I buy them every year (I love sour flavors!) at Fairway. Can't remember the name (if I ever knew it). The kumquats are paler and don't have that cute nub. They are only available briefly this time of year. Oh wait, I think cv's right, it may be a mandarinquat. They're super sour.
It looks a little like calomondin, they are very very astringent and sour. So strong. The calomondin I bought were not quite that orange but looked similar.
Mandarin-quat. Just tried one yesterday. Sour!
looks like a kumquat to me...
They definitely look like the mandarinquats that are sold at my local grocery :-).
I'm guessing they're a variety of kumquat. Are you sure they're not?