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Geological classification of stones

Geologically the stones can be classified as follows:

1) Sedimentary stones:

(a) Characteristics:

Sandstone, limestone, dolomite originally formed mainly in sea water, or lakes, from the remains of animals and plants, also from transportation and deposition of rock products.

A. Formed at or near the surface
B. Distinctive strata
C. Many fossils have been found in this type of rock
Grain shape
A. Rounded
B. Angular

(b) Classification:

.A. Detrital is made from disintigrated pre-existing rock.
B. Biogenetic is made from shells and other fossilized fragments.
C. Chemical is made from chemical precipitation.

2) Metamorphic stones:

(a) Characteristics:

Marble, serpentine, onyx, slate, quartzite, gneiss are produced from sedimentary or igneous rocks by the action of heat and pressure.
A. No pressure - fossils survive
B. Low pressure - fossils distorted or destroyed
C. Moderate pressure - Grains form moderately
D. High pressure - Active fluids may circulate
E. Heat alone, Metamorphic Aureole surrounding a deep plutonic intrusions, possibly with active fluids
F. Dynamic Meta - Large scale movement phenomena
G. Crushing actions produce Xylonite Meta rock from powder
H. Low angle thrust fault: Plate pressure coupled with subsidence
I. Thrust movement, plate movement

(b) Classification:

1. Structure
A. Contact type is crystalline
B. Regional type is usually foliated

2. Grain size
A. +0 Big grain, High pressure
B. 00 Med grain, Med pressure
C. -o Small grain, Low pressure

3. Basic PSI and temperature:

Basic PSI and temperature of occurrence is 480* F - 1472* F 2,000 - 10,000 K