Introduction

Review

Framework silicate = Tectosilicate
Number of O shared per T = 4
Si:O ratio = 1:2
Structural configration = Framework tetrahedra

INTRODUCTION

More than two-thirds of the Earth’s crust is composed of frarnework silicate minerals, because include quartz & feldspar

The structure of all these minerals is based on aframework of TO₄ tetrahredra
– T is Si, or A1 3and each of the 4 oxygen anions is shared with another tetrahedron

Open structure lead to 2 consequences :
1. Composition: easily accommodate large cations (alkaline) due to largest coordination site (O with 6-fold & shear corner) if substitute Si by Al in T site
2. physical properties: law specific gravity (due to Occurrence, occur at law P in crust)