Geology Superstore

Biotite Muscovite Granite

£2.25£6.00 ex VAT

Biotite muscovite granite specimens from St. Austell in Cornwall, UK of Permian age is a coarse grained igneous rock composed of quartz, plagioclase feldspar, biotite and muscovite. The rock is part of the St. Austell pluton which formed 280 million years ago. An off white colour with gold and black flecks of micas, the rock has a unique chemistry and resulted in the rich mineralisation of ores in the area. The samples are suitable for collectors and educational use to show granite variants, available in three sizes. Each piece will come supplied in a card tray with an information label.

  Hurry up! Sale end in:
  •  Delivery & Return


    We ship to all 50 states, Washington DC.
    All orders are shipped with a UPS tracking number.
    Always free shipping for orders over US $200.
    During sale periods and promotions the delivery time may be longer than normal.


    Elessi will accept exchanges and returns of unworn and unwashed garments within 30 days of the date of purchase (14 days during the sales period), on presentation of the original till receipt at any store where the corresponding collection is available within the country of purchase.

    Your return will usually be processed within a week to a week and a half. We’ll send you a Return Notification email to notify you once the return has been completed.
    Please allow 1-3 business days for refunds to be received to the original form of payment once the return has been processed.


    Give us a shout if you have any other questions and/or concerns.
    Phone: +1 (23) 456 789

  ... people are viewing this right now

Guaranteed Safe Checkout

Biotite muscovite granite is coarse grained rock and another variation of granite which is felsic in chemistry, meaning that its main constituent minerals are quartz and feldspar. The quartz has a white colouration which is down to the presence of fluid gases present during the formation of the rock which stop the quartz forming clear. Plagioclase, a potasium mineral being white in general due to either being albite or anorthite gives the rock an overall off white tone in colour. However, this rock also contains numerous biotite and muscovite mica crystals which both contrast in colour from one another due to differing chemistries. Muscovite, like all micas form in sheets and is often colourless when the sheets are single, however, when overlaid can give a bronze or brassy appearance with a hint of green. Biotite mica on the other hand, while almost identical in chemistry, also contains higher amount of iron (Fe), thus, the mineral appears black. All of these minerals together comprise of this rock which is better known as ‘Cornish Granite’. The granite however is part of the Cornubian batholith, specifically the St. Austell pluton, an igneous granitic body which formed during the Permian period around 280 million years ago and was the driving force behind various intrusions of heat and fluid infiltrating the local rock already in the area which resulted in mineralisation and later leading to rich ore deposits. The feldspar from exposed occurrences of this granite and others in the area eventually led to the formation of kalonite which would later be used to produce china clay. An excellent rock specimen for serious collectors as well as college or university level education, these particular rock samples can be used to both describe the variations that one may find in granites as well as show the chemistry of the rock and how such an igneous body can alter it’s surroundings and result in mineral ores being deposited. These samples come from St. Austell in Cornwall, UK and are available in three sizes and come supplied in a card tray with an information label.

Weight 130 g
Specimen Size

2" x 2", 3" x 2", 4" x 3"

Based on 0 reviews

0.00 Overall
Be the first to review “Biotite Muscovite Granite”

Your email address will not be published. Required fields are marked *


There are no reviews yet.

Close My Cart
Close Wishlist
Recently Viewed Close