Man, there is a big amount of nay-saying in this thread.
Here's how I'd do it:
Pech
In the lightless depths of the deep earth live a group of creatures who excel at cleaving it. Sometimes called an elemental, sometimes called a fey -- the distinction is largely academic at this point -- the pechs tunnel their entire life away, chiseling away at stone softer than their own flesh with their tools, and their bare hands.
Intimate with the Earth
While they are flesh and blood, pechs are also rock and stone -- their hard, granite flesh and immense striking power are testament to that. They are born of the rock, and this closeness also enables them to know the weaknesses of the stone from which they are born. They know also where to strike stones the hardest: the natural fault lines and soft points and air pockets invisible to most people are obvious to the pechs. Pechs are also able to shape and enchant stones, with numbers of them banning together to conjure it or to transform it to flesh.
A pech also spends his or her life tunneling. Pech clans wander far and wide through the tunnels of the underdark, expanding them and re-weaving them, opening new ones and digging eternally. They seem to do this out of a primal wanderlust, a need to explore and carve that drives them ever-deeper into the stone they are part of.
Reclusive and Shy
A pech is an elusive creature of the darkness. Mistrustful of outsiders, and not warriors by nature, they prefer to flee than fight. They work well together in a kind of reciprocal, communal relationship, but not so well with outsiders. Pechs are at their most powerful when helped by their allies, so few go anywhere alone.
Simple and Rustic
Pechs are not a people who enjoy a life of luxury or wealth. Though they find many gems and metals in their tunneling, they are resolutely uninterested in such things except as possible trade items. They rarely have more wealth than they can carry, and build little in the way of ornate goods. They are very capable of such things, but they are not very creative individuals, by and large, content to be practical with their powers and their intimacy.
Cultural Details
Alignment: Pechs easily band together and like to help each other, so they tend toward Good. They do rely on each other, rejecting the individualism of Chaos, but their reliance is one more of kinship than of heirarchy, making them poor candidates for Law. On the whole, Pechs are neutral good.
Religion: Pechs don't honor specific deities. Rather, they pay homage to the earth itself, considering themselves born purely of rock. If they are fey, they don't seem to belong to any over-arching court, so their beliefs certainly resemble the elementals more. Some pechs even join up with Sunnis, the Princess of Good Earth Creatures, out of a desire to protect all of their home. This relationship isn't worshipful, however, and resembles more of an alliance under a queen.
Language: Pechs speak Primordial, the ancient and secret language of the elements. Some learn the tongues of others whose lands they may travel through, such as Elven (for dealing with drow), Dwarven, or Gnome.
Names: Pechs take on names based on the rocks they resemble, such as Feldspar, Granite, Obsidian and Limestone. They may or may not translate these names through Primordial first, coming up with some very exotic sounding names that may mean nothing more than "Gravel."
Adventuring Pechs
Pechs who leave the intimacy of their clan and the privacy of their caverns are truly unusual individuals. Still, that wanderlust that drives them to burrow constantly leads some to want to "burrow where there is no earth." These pechs will frequently adopt their adventuring party as a de facto clan, soft and squishy though they might be.
Pech Racial Traits
The following stats are for adventuring pechs, who, having left their clan, have lost the ability to cast pech communal magic. Pechs who are still part of their clan may use more advanced techniques, and pechs PC's may eventually learn how to do that on their own, or with non-pechs, but it is not something they can do at first level.
Size: Small
Speed: 30 ft.
Darkvision: When you are in darkness, you can see up to 60 ft. This ability becomes inactive in areas of light.
Ability Score Adjustment: Your starting Strength score increases by 1.
Skin Like Granite: You have an AC of 13. If you wear armor, use the value of your armor if it is higher.
Stonesplitter: You have Advantage on all attacks against creatures made of rock or stone, or skill checks to work with similar materials.
Stone Shaper: Pechs can work stone with their bare hands, making items from hard rock as if it was soft clay. The rock is still rock (and is still hard and heavy to anyone other than the pech), the pechs are merely able to work it very well. They can create simple tools and items out of the stone, though intricate crafts require intricate craftwork.
Stone Speaker: Pechs can talk to rocks, and the rocks talk back to them. A pech can converse with a stone walkway or a statue or a brick just as one may talk to a neighbor or a friend. Being immobile, and having a very long view of time, the rocks don't often make very sterling conservationists, but pechs can learn information from stones (such as if anyone passed by recently, and a stone's eye view of what they were like).