Guide to Identifying
Terrigenous and Biogenous
Sand Particles
Use with Sand Lab #2
Roundness of Grains
Angular Grain
Well rounded grain
Roundness of grains can give information on how far the sediment has
traveled from it’s source.
Roundness can also give information on how long a sediment has been
residing in a given environment.
Terrigenous Sediments: land derived sediments
• Rocks and minerals.
• Can be continental sediments or
volcanic sediments.
Basalt Sand (terrigenous):
Black to dark gray
Dull to shiny
Angular to rounded
Main component of black sand
Mainly Hawaiian Beaches
Volcanic origin
Usually found with green
olivine grains & volcanic glass.
OLIVINE SAND
Olivine (terrigenous):
Translucent
Glassy
Green to reddishbrown in color
Associated with
basalt volcanoes
Usually found with
basalt and volcanic
glass
Volcanic Glass - (terrigenous):
Also known as obsidian
Associated with volcanic
activity
Usually very angular in shape
with a glassy luster.
Can be translucent if shard is
thin enough.
Quartz Sand – (terrigenous):
Translucent to opaque white
Glassy luster
Angular to rounded grains
Most common mineral in
continental beaches. No volcanic
activity
Quartz can sometimes be stained
red by rust.
Mica Sand
Granite Derived Sands:
Although quartz is the most
common mineral from granite,
mica and garnet are also found in
many sands.
Mica is flat and shiny with a
copper luster
Garnet is deep reddish-brown with
a glassy luster.
Granite
Garnet Sand
Biogenous Sediments: biotic sediments
• Hard parts from living things.
Such as:
– Coral
– Shells
– Spines
– Operculums (cat’s eyes)
– Sponge Spicules
– Plankton shells (bloody
eye)
Coral Fragments:
Can be cream to white in
color
Porous (holes)
Polished
Most of the time the
grains are angular.
Pieces of shells:
-Snail shells
- rounded shell fragments
Snail Operculums
Hydrogenous Sediments - Ooids
Ooids of the
Bahamas
Ooids form in place and are NOT
transported to the beach.
They are hydrogenous sediments
that form similar to a pearl does.
Only found in warm, shallow,
tropical seas without any
terrigenous input (no mountains).
Ooids under the Scope
Creamy, chalky white
grains that are very well
rounded.