8l. If the source of littoral material is uncertain, petrographic 

 analysis may provide evidence by comparison of mineral content on the 

 beach and at possible sources. These sources would include beds of 

 strearrB entering the ocean, friable cliffs subject to wave action, and 

 the beaches themselves. Samples should be about 2^0 cc. in size or about 

 § pint. This size sample will permit both a sieve analysis and micro- 

 scopic examination for mineral content. 



82 „ The first step in the microscopic examination for mineral 

 content is to separate the heavy minerals from the quartz and feldspar. 

 This is accomplished by panning, or by use of heavy liquids, the electro- 

 magnet, or some special method or device. The minor accessories, or 

 so-called "heavy minerals", even though present in very small amounts 

 (tenth of 1 percent or less/ are the important elements in determining 

 source sands and from those an indication of the direction of littoral 

 drift. The next step involves the identification of minerals and determina- 

 tion of the frequency of their occurrence. In this the percentage of 

 heavy minerals in the sample is computed. The heavy minerals are then 

 subdivided down to a quantity sufficient for mounting on a microscopic 

 slide. After identification, the frequencies are determined by actual 

 count or estimation and recorded for comparative purposes, A list of 

 detrital and assocated minerals with comments as to occurrence and stability 

 fol]ows. The direction of littoral drift as indicated by petrographic 

 analysis is determined through comparison of the mineral content and their 

 frequency of occurrence in the beach samples with those in the samples 

 taken from the various sources of beach material. 



Table 8 - Detrital and Associated Minerals 





-iHHt Anatase (c) 



-x-;;-;;- 



Garnet (c) 



-> 



Olivine {r) 



-;k- Andalusite (l) 



■X- 



Glauconite (c) 



-x-x- 



Orthoclase (c) 



''i Apatite (r) 



-;t 



Glaucophane (r) 



-x~x- 



Plagioclase(c) 



** Augite (r) 



-;k4-x- 



Gold (vr) 



'X* 



Pyrite (c) 



-x-x-;;- Barite (r) 



-x-x- 



Gypsum (l) or (aJ 



-x-x- 



Pyrolusite (r) 



-X-* Biotite (l) 



+ 



Hematite (a) 



-X- 



Pyrrhotite (l) 



*->* Brookite (c) 



-x-x- 



Hornblende (c) 



-X-X--X- 



Quartz (c) 



+ Calcite (l) or (a) 



-x-* 



Hypersthene (r) 



-x-x-x- 



Rutile (c) 



■JH«-» Gassiterite (l) 



■«-«• 



Ilmenite (c) 



t 



Siderite (l) or (a) 



iHBi- Chalcedony (c) 



+ 



Kaolinite (a) 



-x-*-;s- 



Sillimanite (l) 



+ Chlorite (c) 



■JhX-X- 



Kyanite (c) 



-x-x-x- 



Spinel (r) 



■sbh;- Ghromite (r) 



*-x-x- 



Leucoxene (c) 



•5HHJ- 



Staurolite (c) 



-x-iH<- Coluinbite (vr) 



+ 



Limonite (a) 



-X-X-K- 



Titanite ir) 



-"'• Cordierite (l) 



-i;-x- 



Marcasite (l) 



-x-j;-x- 



Topaz (c) 



-!HHi- Diamond (vr) 



■iHHJ- 



Magnetite (c) 



-X-X-K- 



Tourmaline (c) 



-x<-x- Epidote (c) or (a) 



-X-X- 



Microcline (l) 



■JHt-X- 



Wolframite (l) 



^HHS- Fluorite (l) 



^HHi- 



Monazite (r) 



*-x-x- 



Xe no time (vr) 





-:i-x-x- 



Muscorite (c) 



■JBHr 



Zircon (c) 



-X^<- 



-s- 



Stable 

 Moderately stable 

 Unstable 



Stable as a secondary 

 product 



(c) Common 



(1) Local 



(r) Rare 



(vr) Very rare 



(a) Alternation product (secondary) 



^7 



