Introduction: rutile is a frequently-observed accessory mineral in igneous (especially intrusive) rocks and as a detrital mineral in sedimentary rocks: it is often present in the metamorphosed equivalents of both. In mineral veins it is less frequent, except in those of the alpine fissure-type, where it is sometimes common, and is invariably associated with quartz, albite, chlorite, apatite, the other TiO₂ polymorphs (anatase and brookite) and rare-earth minerals like synchysite. Rutile is readily identified when well-crystallized owing to its tendency to form dense aggregates of golden hairlike crystals, which when embedded in clear quartz, constitutes the semi-precious gemstone known as sagenite or rutilated quartz. Coarser crystals tend to be darker in colour but again the prismatic to acicular habit and the association is diagnostic.

Occurrence in Wales: early reports of rutile in Wales were limited to descriptions of its occurrence as a rock-forming mineral, as in its presence in the basaltic tuffs of the Bedded Pyroclastic Formation on Lliwedd in the Snowdon range (Williams, 1927). More recently, the attention given to alpine fissure-type veins by mineral collectors has resulted in many more discoveries, which are listed below with references. In igneous rocks, rutile often develops by the breakdown of primary iron-bearing minerals such as ilmenite, as described in dolerites from the Preseli hills of SW Wales by Ixer (in Thorpe et al., 1991) and at Parys Mountain on Anglesey (Pointon & Ixer, 1980). A common product of such a reaction is a mixture of quartz and rutile which is generally referred to as leucoxene.

Last saved full search

Alphabetical search:

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z