It may be hard to find two snowflakes that look identical, but you can classify snow crystals according to their shapes. This is a list of different snowflake patterns.
Hexagonal PlatesThis snowflake exhibits hexagonal plate crystal structure. Wilson A. Bentley
Hexagonal plates are six-sides flat shapes. The plates may be simple hexagons or they may be patterned. Sometimes you can see a star pattern in the center of a hexagonal plate.
Stellar PlatesThis is an example of a snowflake with a stellar plate shape. fwwidall, Getty Images
These shapes are more common than the simple hexagons. The term 'stellar' is applied to any snowflake shape that radiates outward, like a star. Stellar plates are hexagonal plates that have bumps or simple, unbranched arms.
Stellar DendritesWhen most people envision a snowflake, they think of a lacy stellar dendrite shape. These snowflakes are common, but many other shapes are found in nature. Wilson A. Bentley
Stellar dendrites are a common snowflake shape. These are the branching six-sided shapes most people associate with snowflakes.
Fernlike Stellar DendritesThis snowflake exhibits a fernlike dendritic crystal shape. Wilson A. Bentley
If the branches extending from a snowflake look feathery or like the fronds of a fern, then the snowflakes are categorized as fernlike stellar dendrites.
NeedlesNeedles are slender columnar ice crystals that tend to form when the temperature is around -5 degrees Celsius. The large photo is an electron micrograph. The inset is a light micrograph. USDA Beltsville Agricultural Research Center
Snow sometimes occurs as fine needles. The needles may be solid, hollow, or partially hollow. Snow crystals tend to form needle shapes when the temperature is around -5°C.
ColumnsSome snowflakes have a columnar shape. The columns are six-sided. They may have caps or no caps. Twisted columns also occur. USDA Beltsville Agricultural Research Station
Some snowflakes are six-sided columns. The columns may be short and squat or long and thin. Some columns may be capped. Sometimes (rarely) the columns are twisted. Twisted columns are also called Tsuzumi-shaped snow crystals.
BulletsColumn and bullet snowflakes can grow across a wide range of temperatures. Sometimes the bullets may be joined to form rosettes. These are electron micrographs and light micrographs. USDA Beltsville Agricultural Research Center
Column-shaped snowflakes sometimes taper at one end, forming a bullet shape. When the bullet-shaped crystals are joined together they can form icy rosettes.
Irregular ShapesAlthough there are many photos of perfect-looking snowflakes, most flakes exhibit irregular crystalline forms. Also, many snowflakes are three-dimensional, not flat structures. USDA Beltsville Agricultural Research Center
Most snowflakes are imperfect. They may have grown unevenly, broken, melted and refrozen, or had contact with other crystals.
Rimed CrystalsThere is a snowflake somewhere under all this rime; you can barely make out its shape. Rime is frost that forms from water vapor around the original crystal. USDA Beltsville Agricultural Research Station
Sometimes snow crystals come in contact with water vapor from clouds or warmer air. When the water freezes onto the original crystal it forms a coating that is known as rime. Sometimes rime appears as dots or spots on a snowflake. Sometimes rime completely covers the crystal. A crystal coated with rime is called graupel.