Almandine is one of the garnets. The most common of them.
Its ideal composition is Fe3Al2(SiO4)3. Fe can be replaced with Mg or Mn. If there is Mg more than Fe, we call this garnet pyrope. If there is more Mn than Fe, then it is spessartine. There are more garnet varieties but they do not form continuous solid solutions with the three mentioned above.
Almandine is a common mineral in metamorphic rocks, mostly schists and gneiss. But it is a usual constituent of felsic igneous rocks too.
Almandine is very common in sands heavy mineral fraction. It is so widespread because it is a major component of several rock types and moderately resistant to the weathering. It is among the most beautiful minerals one can see in sand. If you notice pink grain, it most likely is almandine. However, it may also have darker red color. The composition is not fixed and therefore there is no single identifiable color.
It is not too hard to distinguish garnet from other minerals because it is isotropic. You still need a polarizing microscope though. But there is really no sure and easy method to say what type of garnet it is. Color might be a good indicator. Spessartine tends to have more yellowish colors and pyrope is dark red or even purplish. However, color is often misleading indicator. So it probably is better to call these reddish grains garnets without attempting to specify. Things might get more complicated because there are some insiduous minerals that may be misidentified as garnet. These are staurolite and red chrome-bearing spinel.
Almandine is the most common of garnets. These crystals contain some magnesium which puts them part way into the pyrope group. That might also explain darker red color. Thanks to Bill Beiriger for these beautiful crystals.
