FOURTH SUPPLEMENTARY TARGET’S STATEMENTDear Fellow...

FOURTH SUPPLEMENTARY TARGET’S STATEMENT

Dear Fellow Shareholder

YOUR DIRECTORS UNANIMOUSLY RECOMMEND THAT YOU
REJECT SKAFELL’S REVISED OFFER OF 77.5c

The Directors of Tethyan Copper Company Limited have carefully considered the revised offer for the
acquisition of all of your shares in Tethyan that was announced by Skafell Pty Limited on 17 January
2006.

As we advised the market yesterday, your Directors have unanimously concluded that the revised offer
remains inadequate and significantly undervalues your shares.
In reaching their decision to REJECT the increased offer, your directors considered a range of issues
including the following:

• The value impact of the recent doubling in the total mineral resources identified at Reko Diq.

• The value that can be inferred for your shares by the proposed transaction with Antofagasta
Plc – a transaction that your directors continue to unanimously support.

• The market price of Tethyan shares – as we describe in more detail below, your directors
believe that Skafell’s offer is continuing to hold back the value of Tethyan’s shares.

Taking these and all other relevant factors into account, your Directors unanimously
recommend that you continue to reject Skafell’s offer. To do so, simply ignore all
correspondence you receive from Skafell or Crosby.

Your Directors do not intend to accept the offer for any of the shares they own or control.

Your Directors intend to continue with the implementation of the Antofagasta Transaction
and will recommend that you vote in favour of the resolution relating to that transaction.

We are now finalising the Notice of Meeting and Explanatory Memorandum, which will be mailed to you
shortly. This will provide shareholders with the opportunity to consider and vote on the proposed
Antofagasta Transaction.

As previously announced, Tethyan also intends to apply to have its securities listed on the AIM market
in London, with the listing likely to occur shortly after the shareholders meeting planned for late
February 2006.

Comments on Skafell’s 6th Supplementary Bidder’s Statement

In its latest supplementary bidder’s statement, Skafell repeats a number of assertions that it has made
in numerous previous attempts to denigrate your Company. It is worth remembering that Skafell is
acting only in its own interests and is attempting to acquire your Company for less than what your
Directors consider it is worth. Skafell’s ongoing, and in many cases misleading, attacks on your
Company must be seen for what they are – self serving comments designed to further its own
interests, which are not the same as yours. Crosby’s interests are to buy your shares at the lowest price
that they can get them for.

Skafell’s latest offer is inadequate

Skafell’s increased offer of A$0.775 represents a negligible premium of 3.3% to the closing price of
your shares on the day immediately preceding their offer (closing price on 16 January 2006: A$0.75 per
Tethyan share) and a 21% premium over their previous offer.

You should also note that Skafell’s offer is at a discount of 6.6% to the price that Antofagasta – a
major copper mining company – is willing to pay for a non-controlling stake in Tethyan.
More importantly, in the seven month period since Skafell’s initial inadequate offer was announced in
May 2005, there have been significant improvements to the mineral resources at Reko Diq and to
relevant commodity prices:

• the copper price has increased 46% to US$2.16/lb;
• the gold price has increased 34% to US$559 per ounce;
• the total Reko Diq mineral resource has increased by 156%; and
• the proportion of this mineral resource in the higher-level Indicated Resource
category has increased from 16% to 53% of the total (expanded) mineral resource.

Your Directors believe that the Skafell bid has prevented these changes from flowing through into
Tethyan’s share price – effectively stifling the share price through seven months of a major copper
boom. Indeed, your Director’s believe that Skafell improved its bid now, after 7 months of inaction, at
least partly in order to again cap the share price before it could move any higher.

A comparison of Tethyan’s share price with the ASX 200 Resources Index and the copper price, since
the initial offer was announced in May 2005, demonstrates the stifling effect the Crosby bid has had on
Tethyan’s share price.

Skafell’s repeated assertions that the Antofagasta Transaction is dilutionary are misleading

Skafell asserts that as a result of the Antofagasta Transaction “Tethyan will hold only 50% of assets in
which the Company previously held a 100% interest” and that Tethyan shareholders interests in the
Reko Diq will be “diluted by a massive c. 60%, …”. These statements are misleading. Skafell ignores
both the 25% interest in Reko Diq already held by the Government of Balochistan, and the existence of
the BHP Billiton Clawback Right.

The Antofagasta Transaction provides Tethyan with the means to terminate the BHP Billiton Clawback
Right, thereby clarifying the ownership structure of the Reko Diq Project and increasing Tethyan’s
interests in the Reko Diq Project by comparison to the interests it would hold if the Clawback Right
were exercised.

After taking account of the issue of shares to Antofagasta (approximately 17.3% of Tethyan’s fully
diluted share capital) and the creation of the 50:50 joint venture, the ownership interest of Tethyan’s
shareholders in the copper and gold at Reko Diq will increase by 10% for copper and 38% for
gold, by comparison to shareholders’ ownership interests if the Clawback Right were exercised in the
absence of the Antofagasta Transaction.

To put it another way, the Antofagasta Transaction will increase the amount of copper per Tethyan
share from the current 48 pounds of copper per Tethyan share if the Clawback Right were exercised, to
53 pounds of copper per Tethyan share after the Antofagasta Transaction. The equivalent figures for
gold are 0.96 grams per share rising to 1.32 grams per share.

The ownership interests of Tethyan’s shareholders (taking account of both the issue of shares to
Antofagasta and the creation of the joint venture) before and after the Antofagasta Transaction is
represented below:

In summary, your Directors agree with Skafell that shareholders face a stark choice – an early and
inadequate cash exit (assuming the Skafell takeover offer becomes unconditional), leaving all the future
value of the Reko Diq project to Skafell; or the Antofagasta Transaction – a 50:50 joint venture with a
major copper mining company that actually increases shareholder’s effective ownership interests
through the termination of the Clawback Right, and provides a free carry for shareholders for up to the
next US$75 million of expenditure – in your Director’s view a remarkably favourable basis on which to
continue your participation in the global commodity boom via a Project that only 2 weeks ago was
demonstrated to be among the world’s 25 largest copper projects (on a copper-equivalent basis).
In all the circumstances, Tethyan’s Directors urge shareholders to continue to reject Skafell’s revised
offer and to take no action with regard to any correspondence from Skafell.
_________________________
David Humann
Chairman
Dated: 19 January 2006