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 reddish-brown 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.

Granite Derived Sands: 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

Urchin spines suggest a rocky beach habitat Urchin spines suggest a rocky beach habitat. Purple spines are found in temperate areas where striped are tropical.

Snail Operculum

Foraminifera-Plankton Shells Tiny shell-like sediments that can be found anywhere. Foraminifera

More Foram Sand (plankton shells) “Bloody Eye” foram shells Sponge Spicule

Sand from Bali Predominately plankton shells Snail Shell Urchin Spine

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.